Yellow fever “lives” mainly on the African and South American continents. The symptoms resemble ordinary jaundice. Accompanied by high fever and bleeding. Fifty percent of unvaccinated people are more likely to die. Regular aspirin can cause severe bleeding and death.

What is yellow fever

The fever manifests itself in outbreaks in certain regions. Massive infection of people was observed in South Africa, Central and South America.

In total, during the appearance of the disease in these territories, approximately 170,000 cases of the disease were recorded, of which 60,000 were fatal.

Antiviral drugs that eliminate fever have not been found to date.

The causative agent of the disease

Virus has good endurance at low and high temperatures. In a frozen environment, its infectious properties can persist for up to nine months. But in hot conditions the virus is not very comfortable. At temperatures exceeding 60 degrees and under the influence of ultraviolet radiation, the adenovirus dies. If you boil it, after a couple of seconds there will be nothing left of it.

The causative agent of yellow disease requires a living environment for constant reproduction. These are animal and human cells. When it enters the body, the virus settles in the tissues of the liver, kidneys, lungs, lymph nodes, spleen, myocardium, bone marrow, blood vessels, and brain. In a word, the whole organism is damaged.

Causes of yellow fever. How the disease develops

Mosquitoes transmit adenovirus through their bite. An infected mosquito becomes dangerous to humans around the ninth day. It all depends on the temperature conditions. The higher it is, the more intensely the disease begins to progress. Infected insects that enter an area where the air temperature is less than 18 degrees will not be able to transmit the virus.

Animals also become infected from mosquitoes. People who come on an excursion to the tropics, visiting the jungle, automatically fall into a risk group.

Before traveling to countries in Africa, Central and South America, you must undergo a WHO-approved vaccination.

Symptoms and signs of yellow fever

Yellow fever occurs in three main stages:

• Elementary.
• Period of improvement (remission).
• Period of deterioration (venous stasis).

• sensation;
• constant chills;
• dry mouth;
• repeated vomiting;
• and dry;
• and limbs become stronger;
• the heart rate is muffled, the pulse quickens;
• blood pressure remains normal against this background;
• redness of the face and neck;
• tearfulness of the eyes and swelling of the eyelids.

On initial examination, an enlarged liver and kidneys are observed. ESR in the blood does not increase.

On the third day, the patient exhibits symptoms of jaundice. Yellowness affects the whites of the eyes, eyelids, and then the skin and mucous membranes of the mouth.

Yellow fever in the first stage can occur in different ways. With poor immunity, the patient begins to bleed from the nose and gums. An admixture of blood clots can also be seen in the vomit.

If help is not provided to the patient in a timely manner, the person dies at the initial stage of the disease.

Deterioration of condition called period of venous stagnation. This is the most dangerous moment. Body temperature rises again. Jaundice progresses. Hemorrhagic syndrome manifests itself in full force: uterine, nasal and other bleeding appears. In this case, a sharp drop in blood pressure is observed.

Laboratory studies indicate an increase in blood ESR and a decrease in leukocyte levels to a critical level. In this condition, blood does not clot well. The protein in the urine exceeds the permissible limits several times.

Patients successfully survive the third stage of the disease only in 50% of cases. The rest die. Coma occurs due to renal failure, resulting in cerebral edema with loss of consciousness, from which the patient never returns.

If you do not seek help in a timely manner, the disease may be recognized as jaundice. The treatment prescribed in this case will only worsen the patient’s situation, and death will occur quite quickly.

Diagnosis of yellow fever

The difficulty of diagnosing yellow fever is that its symptoms are similar to viral hepatitis, influenza, tropical malaria and other types of fever. At the first stage, disease prediction begins with laboratory tests. Blood and urine are collected for analysis.

A biochemical blood test indicates elevated levels bilirubin, responsible for the breakdown of hemoglobin in the blood. To identify the pathogen, animal samples are performed in the laboratory.

Yellow fever affects almost all organs. During the first period of the disease there is renal failure And liver enlargement.

Treatment of yellow fever

Modern scientists are working on drugs to get rid of yellow fever, but so far to no avail. Therefore, treatment is aimed at easing the course of the disease. The patient's immunity is supported. A high-calorie diet is prescribed. Food should be liquid and easily digestible by the body. The patient is supported with vitamins C, P, K. Depending on the complexity of the disease, blood transfusions are prescribed every two days.

The preparations are based on bovine liver extract. Patients receive iron intramuscularly. Such therapy is necessary to compensate for blood loss. Glucose is administered intravenously.

Depending on the condition of the internal organs, the patient is prescribed anti-inflammatory, antihistamine, and cardiovascular drugs. Often it is necessary to resort to resuscitation of the patient.

You should not treat yourself. One tablet of regular aspirin for yellow fever will cost you your life!

• Kidney failure.
• Pneumonia.
• Heart rhythm disturbance.
• Encephalitis – brain damage.
• Gangrene of the limbs and soft tissues.

Prevention and vaccinations

People planning travel and business trips to tropical countries must undergo mandatory vaccination. You must have insect repellent with you.

In countries at risk of epidemics, a set of measures is being carried out aimed at exterminating insects in places where they are numerous, in particular in residential areas.

If you are planning a trip to the tropics, take care in advance to maintain your immunity with the help of special medications.

On the official WHO website you can find out which countries you need to get vaccinated before traveling to. There is only one type of live vaccine in Russia, is inexpensive - on average 2500 rubles. Vaccinations are allowed for everyone from the age of nine months.

An injection is given under the shoulder blade in the amount of 0.5 ml of vaccine, regardless of age. Immunity begins to develop on the tenth day. Revaccination will be required after ten years, in which case the person is protected from the first day.

After receiving the vaccination, a person is issued an “International Vaccination Certificate”.

Yellow fever– an acute natural focal viral infection characterized by a severe course with a predominance of intoxication, icteric and hemorrhagic syndrome. Yellow fever is one of the most dangerous infections. Yellow fever is spread by vectors and is carried by mosquitoes. The incubation period for yellow fever is about a week. its clinical picture includes severe intoxication up to disturbances of consciousness and cardiac activity, hemorrhagic syndrome, hepatosplenomegaly, yellowness of the sclera. Treatment of a patient with yellow fever is carried out exclusively inpatiently in the department for especially dangerous infections.

General information

Yellow fever– an acute natural focal viral infection characterized by a severe course with a predominance of intoxication, icteric and hemorrhagic syndrome. Yellow fever is one of the most dangerous infections.

Characteristics of the pathogen

The yellow fever virus is an RNA-containing virus, belongs to the genus Flavivirus, and is stable in the external environment. It tolerates freezing well and dies within 10 minutes when heated to 60 °C, and is also easily inactivated by ultraviolet radiation and disinfectant solutions. Does not tolerate acidic environments well. The reservoir and source of infection are animals - monkeys, marsupials, rodents and insectivores. A person can become a source of infection only if there is a carrier.

The disease spreads through a vector-borne mechanism; the virus is transmitted by mosquitoes. In the Americas, yellow fever is spread by mosquitoes of the genus Haetagogus, in Africa - by Aedes (mainly the species A. Aegypti). Mosquitoes breed near human dwellings, in barrels of water, artificial stagnant reservoirs, flooded basements, etc. Insects are infectious from 9-12 days after biting a sick animal or person at a temperature of 25 °C and after 4 days at 37 °C. Transmission of the virus does not occur at ambient temperatures less than 18 °C.

If blood containing the pathogen gets into areas of damaged skin or mucous membranes, a contact route of infection may occur (when processing the carcasses of sick animals). People have a high natural susceptibility to infection; after exposure, long-term immunity is formed. The disease is classified as a quarantine disease (due to its special danger); cases of yellow fever epidemics are subject to international registration.

Outbreaks of the disease can occur in any zone of the vector's distribution range, predominantly occurring in tropical countries. The spread of fever from the source of the epidemic occurs when patients move and mosquitoes move during the transportation of goods. Yellow fever epidemics develop in the presence of three necessary conditions: carriers of the virus, vectors and favorable weather conditions.

Pathogenesis of yellow fever

The virus enters the blood during blood sucking from the digestive system of the carrier and, during the incubation period, reproduces and accumulates in the lymph nodes. During the first days of the disease, the virus spreads throughout the body through the bloodstream, settling in the tissues of various organs (liver and spleen, kidneys, bone marrow, heart muscle and brain) and affecting their vascular system and causing inflammation. As a result of disruption of trophism and the direct toxic effect of the virus, necrotic destruction of the parenchyma occurs, and increased permeability of the vascular wall contributes to hemorrhage.

Symptoms of yellow fever

The incubation period for yellow fever is a week (sometimes 10 days). The disease occurs with a change of successive phases: hyperemia, short-term remission, venous stasis and convalescence. The hyperemia phase begins with a sharp rise in temperature, increasing intoxication (headache, body aches, nausea and vomiting of central origin). As the intoxication syndrome progresses, central nervous system disorders may occur: delusions, hallucinations, and disturbances of consciousness. The patient's face, neck and shoulder girdle are puffy, hyperemic, there are numerous scleral injections, the mucous membranes of the mouth, tongue, and conjunctiva are bright red. Patients complain of photophobia and lacrimation.

Toxic cardiac disorders are noted: tachycardia alternating with bradycardia, hypotension. The amount of daily urine decreases (oliguria), and a moderate increase in the size of the spleen and liver is noted. Subsequently, the first signs of developing hemorrhagic syndrome appear (hemorrhages, bleeding), the sclera acquires an icteric tint.

The hyperemia phase lasts about 3-4 days, after which a short-term remission occurs (lasting from several hours to a couple of days). The temperature normalizes, the general well-being and objective condition of the patients improves. With abortive forms of yellow fever, recovery subsequently occurs, but most often, after a short-term remission, the body temperature rises again. In general, the febrile period is usually 8-10 days from the onset of the disease. In severe cases, after a short-term remission, a phase of venous stasis begins, manifested by pronounced pallor and cyanotic skin, rapidly developing jaundice, petechiae, ecchymatoses, and purpura are common. Hepatosplenomegaly occurs.

The condition of the patients worsens significantly, hemorrhagic symptoms are expressed, patients note vomiting with blood, melena (tarry stool is a sign of intense intestinal bleeding), nosebleeds, and internal hemorrhages may occur. Oliguria usually progresses (up to anuria), and bloody impurities are also noted in the urine. In half of the cases, the disease progresses with the development of severe lethal complications. With a favorable course, a long period of convalescence occurs, clinical symptoms gradually regress. It is possible that various functional disorders may persist with significant tissue destruction. After surviving the disease, lifelong immunity is maintained, and no recurrent episodes are observed.

Severe yellow fever can be complicated by infectious-toxic shock, renal and liver failure. These complications require intensive care measures, in many cases leading to death on the 7th-9th day of the disease. In addition, encephalitis may develop.

Diagnosis of yellow fever

In the first days, a general blood test shows leukopenia with a shift in the leukocyte formula to the left, a decreased concentration of neutrophils and platelets. Subsequently, leukocytosis develops. Thrombocytopenia progresses. The hematocrit increases, the content of nitrogen and potassium in the blood increases. A general urine test reveals an increase in protein, red blood cells and columnar epithelial cells are noted.

A biochemical blood test shows an increase in the amount of bilirubin and the activity of liver enzymes (mainly AST). Isolation of the pathogen is carried out in specialized laboratories, taking into account the special danger of infection. Diagnosis is made using a bioassay on laboratory animals. Serological diagnosis is carried out using the following methods: RNGA, RSK. ELISA. RNIF and RTNG.

Treatment of yellow fever

Yellow fever is treated inpatiently in an infectious diseases department, specialized for the treatment of particularly dangerous infections. At present, no etiotropic therapy for this disease has been developed; treatment is aimed at maintaining immune functions, pathogenetic mechanisms and alleviating symptoms. Patients are prescribed bed rest, semi-liquid, easily digestible food rich in calories, and vitamin therapy (vitamins C, P, K). In the first days, plasma transfusions from convalescent donors can be performed (the therapeutic effect is insignificant).

During the period of fever, patients are transfused with blood in the amount of 125-150 ml every 2 days, drugs based on bovine liver extract are prescribed, iron is given intramuscularly to compensate for blood loss. In complex therapy, anti-inflammatory drugs (if necessary, corticosteroids), antihistamines, hemostatic agents, and cardiovascular drugs can be prescribed. If necessary, resuscitation measures are carried out.

Forecast and prevention of yellow fever

The prognosis for yellow fever in the case of a mild or abortive course is favorable, but with the development of a severe clinical course it gets worse. Complications of infection lead to death in half of the cases.

Disease prevention involves monitoring population migration and cargo transportation in order to eliminate the possibility of yellow fever being imported from the epidemic focus. In addition, yellow fever vectors are being exterminated in populated areas. Individual prevention involves the use of protection against insect bites. Specific prevention (vaccination) consists of administering a live attenuated vaccine. Immunoprophylaxis is indicated for persons of any age planning to travel to endemic regions 7-10 days before departure.

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Yellow fever

What is Yellow Fever -

Yellow fever(yellow fever, fievre jaune, fiebre amarilla, vomito negro, febris flava) is an acute obligate-transmissible disease with natural focality from the group of viral hemorrhagic fevers. Refers to particularly dangerous infections. Characterized by a severe course with high fever, liver and kidney damage, jaundice, and bleeding from the gastrointestinal tract. The clinical picture of yellow fever was first described during an outbreak in America in 1648. In the 17th-19th centuries, numerous epidemics were recorded in Africa and South America, and outbreaks of the disease in southern Europe. The vector-borne route of transmission of infection through Aedes aegypti mosquitoes was established by K. Finlay (1881), its viral etiology was established by W. Reed and D. Carroll (1901). The natural focality of the disease, the role of monkeys in the circulation of the pathogen in the foci was established by the studies of Stokes (1928) and Soper et al. (1933). In 1936, Lloyd et al. developed an effective vaccine against yellow fever.

What provokes / Causes of Yellow fever:

The causative agent of yellow fever- RNA genomic virus Viscerophilus tropicus of the Flavivirus genus of the Flaviviridae family. The diameter of viral particles is 17-25 nm. It is antigenically related to the Japanese encephalitis and dengue fever viruses. Pathogenic to monkeys, white mice and guinea pigs. Cultivated in developing chick embryos and tissue cultures. It is stored for a long time (more than a year) in a frozen state and when dried, but at 60 ° C it is inactivated within 10 minutes. It quickly dies under the influence of ultraviolet rays, ether, and chlorine-containing drugs in normal concentrations. Low pH values ​​have a detrimental effect on it. Populations at risk of yellow fever The population of 45 endemic countries in Africa and Latin America, totaling more than 900 million people, is at risk. In Africa, an estimated 508 million people living in 32 countries are at risk. The remaining populations at risk live in 13 Latin American countries, with Bolivia, Brazil, Colombia, Peru and Ecuador most at risk. An estimated 200,000 cases of yellow fever occur worldwide each year (30,000 of which are fatal). A small number of imported cases occur in countries free of yellow fever. Although the disease has never been introduced into Asia, the region is at risk because it has the conditions necessary for transmission. Reservoir and sources of infection- various animals (monkeys, marsupials, hedgehogs, possibly rodents, etc.). In the absence of a carrier, a sick person is not dangerous to others. Transmission mechanism- transmission. The carriers are mosquitoes of the genera Haetagogus (on the American continent) and Aedes, especially A. aegypti (in Africa), which have a close connection with human habitation. Vectors breed in decorative ponds, water barrels, and other temporary water reservoirs. They often attack humans. Mosquitoes become infectious within 9-12 days after blood-sucking at ambient temperatures up to 25°C and after 4 days at 37°C. At temperatures below 18 °C, the mosquito loses its ability to transmit the virus. If infected blood comes into contact with damaged skin and mucous membranes, a contact route of infection is possible. Natural receptivity people are high, post-infectious immunity is long-lasting. Main epidemiological features. Yellow fever is classified as a quarantine disease (a particularly dangerous disease) subject to international registration. The highest incidence is recorded in tropical areas, but outbreaks of this disease occur almost everywhere where there are carriers of the virus. The spread of the virus from endemic areas can occur both through sick individuals and through mosquitoes during the transportation of goods. There are two types of foci: natural (jungle) and urban (anthropurgic). The latter more often manifest themselves in the form of epidemics; in this case, the sources of infection are patients during the period of viremia. In recent years, yellow fever has become more of an urban disease and has acquired the features of anthroponosis (transmission occurs through the chain “human - mosquito - human”). If there are conditions for the spread of the pathogen (virus carriers, a large number of carriers and susceptible individuals), yellow fever can become epidemic.

Pathogenesis (what happens?) during Yellow Fever:

Reproduction of the virus that enters the body through a mosquito bite occurs in regional lymph nodes during the incubation period. During the first few days of illness, the virus disseminates through the bloodstream throughout the body, causing damage to the vascular apparatus of the liver, kidneys, spleen, bone marrow, myocardium, brain and other organs. They develop pronounced dystrophic, necrobiotic, hemorrhagic and inflammatory changes. Characterized by multiple hemorrhages in the gastrointestinal tract, pleura and lungs, as well as perivascular infiltrates in the brain.

Symptoms of Yellow Fever:

There are three variants of yellow fever in humans. These are jungle fever (rural type), city fever and an intermediate type. Rural option(yellow jungle fever). In tropical forests (selva), yellow fever occurs in monkeys infected by the bites of “wild” mosquitoes. Infected monkeys can spread the infection by passing it on to healthy mosquitoes. Infected "wild" mosquitoes bite and transmit the virus to people in the forest. This chain leads to isolated cases of infection, mainly in young people working in logging, without leading to epidemics or large outbreaks. The infection can also spread between infected people. Intermediate option infection occurs in humid or semi-humid African savannas and is the dominant form of infection on the continent. There are limited-scale epidemics that differ from the urban variant of the infection. “Semi-domestic” mosquitoes infect both animals and people. During such epidemics, several villages can be affected simultaneously, but the mortality rate with this variant of yellow fever is lower than with urban ones. Urban option infections are accompanied by large-scale epidemics, which are caused by the influx of migrants into urbanized regions with high population densities. “Domestic mosquitoes” (species Aedes aegypti) transmit the virus from person to person; monkeys are not involved in the epidemic chain of transmission of the disease. Incubation period lasts about a week, occasionally up to 10 days. In typical cases, the disease goes through several successive stages. Hyperemia phase. The acute onset of the disease is manifested by a rapid increase in body temperature above 38 °C with chills, headache, myalgia, pain in the back muscles, nausea and vomiting, agitation and delirium. In the dynamics of this phase of the disease, these symptoms persist and intensify. When examining patients, hyperemia and puffiness of the face, neck, shoulder girdle, bright hyperemia of the vessels of the sclera and conjunctiva, photophobia, and lacrimation are noted. Hyperemia of the tongue and oral mucosa is very characteristic. Severe tachycardia persists in severe cases of the disease or is quickly replaced by bradycardia, and initial arterial hypertension is replaced by hypotension. The size of the liver and, less commonly, the spleen increase slightly. Oliguria, albuminuria, and leukopenia occur. Cyanosis, petechiae appear, and symptoms of bleeding develop. At the end of the phase, icterus of the sclera may be noted. The duration of the hyperemia phase is 3-4 days. Short-term remission. Lasts from several hours to 1-2 days. At this time, the body temperature usually decreases (down to normal values), the well-being and condition of the patients improve somewhat. In some cases, with mild and abortive forms, recovery gradually occurs in the future. However, more often, after a short-term remission, high fever occurs again, which can last up to 8-10 days, counting from the onset of the disease. In severe cases, remission is replaced by a period of venous stasis. During this period, there is no viremia, but fever persists, pallor and cyanosis of the skin, icteric staining of the sclera, conjunctiva and soft palate are noted. The patient's condition worsens, cyanosis, as well as jaundice, progress rapidly. Widespread petechiae, purpura, and ecchymosis occur. Hepatolienal syndrome is pronounced. Characterized by vomiting blood, melena, bleeding gums, and organ bleeding. Oliguria or anuria and azotemia develop. Infectious-toxic shock and encephalitis are possible. Infectious-toxic shock, renal and liver failure lead to the death of patients on the 7-9th day of illness. Complications infections can be pneumonia, myocarditis, gangrene of soft tissues or extremities, sepsis as a result of the layering of a secondary bacterial infection. In cases of recovery, a long period of convalescence develops. Post-infectious immunity is lifelong.

Diagnosis of Yellow Fever:

In Ukraine, yellow fever can only occur in the form of imported cases. In clinical differential diagnosis, attention is paid to the sequential change of the main two phases in the development of the disease - hyperemia and venous stasis - with a possible short period of remission between them. Laboratory data The initial stage of the disease is characterized by leukopenia with a sharp shift to the left, neutropenia, thrombocytopenia, at its height - leukocytosis, progressive thrombocytopenia, increased hematocrit, blood nitrogen and potassium. The amount of protein in the urine increases, red blood cells and casts appear. Hyperbilirubinemia and high activity of aminotransferases (mainly AST) are noted. In specialized laboratories, it is possible to isolate the virus from the blood in the initial period, using biological diagnostic methods (infection of newborn mice). Antibodies to the virus are determined using RNGA, RSK, RNIF, indirect hemagglutination inhibition reaction, ELISA.

Treatment of Yellow Fever:

Treatment of yellow fever is carried out according to the same principles as hemorrhagic fever with renal syndrome, in the conditions of infectious diseases departments for working with especially dangerous infections. Causal therapy has not been developed. Convalescent blood plasma, used in the first days of illness, gives a weak therapeutic effect. Forecast: the mortality rate of the disease ranges from 5%-10% to 15-20%, and during epidemic outbreaks - up to 50-60%.

Prevention of Yellow Fever:

Preventive actions are aimed at preventing the introduction of the pathogen from abroad and are based on compliance with the International Health Regulations and the Rules for the sanitary protection of the territory. They destroy mosquitoes and their breeding sites, protect premises from them and use personal protective equipment. Specific tests are carried out at foci of infection immunoprophylaxis with live attenuated vaccine. It is administered subcutaneously to persons of all ages in a volume of 0.5 ml. Immunity develops within one week in 95% of vaccinated people. Immunity develops after 7-10 days and lasts for at least 10 years. Vaccination of children and adults is carried out before leaving for endemic areas (South Africa), where the disease in new arrivals is very severe and has a high mortality rate. Immunization against yellow fever is recommended:- persons traveling on business or tourism (even for a short time), or living in a region where the disease is endemic, - unvaccinated persons traveling from an endemic to a non-endemic region. In accordance with the established rules, a stamp of vaccination against yellow fever must be affixed to the International Certificate, as well as signed and approved by an accredited yellow fever vaccination center. - This vaccination certificate is valid for 10 years, starting from the 10th day after the date of vaccination. - persons at risk of infection due to their professional duties, HIV-infected persons in the asymptomatic stage. In accordance with established rules, a mark on vaccination against yellow fever must be affixed to the International Certificate, as well as signed and approved by an accredited yellow fever vaccination center. This vaccination certificate is valid for 10 years, starting on the 10th day after the date of vaccination. Contraindications to vaccination against yellow fever: General contraindications for yellow fever vaccination are similar to those for any vaccination: - infectious diseases in the active stage, - progressive malignant diseases, - current immunosuppressive therapy. Specific contraindications: - documented allergy to egg whites, - acquired or congenital immunodeficiency. Pregnant women and children under 6 months of age are not recommended to be vaccinated. However, in the event of an epidemic, pregnant women and infants from 4 months of age can be vaccinated. In difficult cases, you should consult a doctor. Precautions for yellow fever vaccination- In persons with allergic diseases, a test is indicated to assess sensitivity to the drug by intradermal administration of 0.1 ml of the vaccine. If there are no reactions within 10 - 15 minutes, the remaining 0.4 ml of vaccine should be administered subcutaneously. - In special cases, a decision may be made to vaccinate patients receiving immunosuppressive therapy. It is best not to vaccinate until 1 month after the end of such therapy and, in any case, you should make sure that the biological indicators are within normal limits. - In difficult cases, you should consult a doctor. Adverse reactions Sometimes, 4-7 days after vaccination, general reactions may occur - headache, malaise, slight increase in body temperature. Activities in the epidemic outbreak Patients are hospitalized in the infectious diseases department. If a sick person is detected on a ship during a voyage, he is isolated in a separate cabin. Disinfection is not carried out in the outbreak. Any vehicle arriving from countries affected by yellow fever must have information about the disinfestation carried out. Unvaccinated persons arriving from endemic areas are subject to isolation with medical supervision for 9 days. If an outbreak of yellow fever occurs, mass immunization of the population begins immediately. List of countries requiring an international certificate of vaccination against yellow fever. 1. Benin 2. Burkina Faso 3. Gabon 4. Ghana 5. Democratic Republic of the Congo 6. Cameroon 7. Congo 8. Ivory Coast 9. Liberia 10. Mauritania 11. Mali 12. Niger 13. Peru (only when visiting jungle areas) 14. Rwanda 15. Sao Tome and Principe 16. Togo 17. French Guiana 18. Central African Republic 19. Bolivia List of countries with zones endemic for this infection, upon entry to which it is recommended to have an international certificate of vaccination against yellow fever : South American countries 1. Venezuela 2. Bolivia 3. Brazil 4. Guyana 5. Colombia 6. Panama 7. Suriname 8. Ecuador African countries 1. Angola 2. Burundi 3. Gambia 4. Guinea 5. Guinea-Bissau 6. Zambia 7. Kenya 8. Nigeria 9. Senegal 10. Somalia 11. Sudan 12. Sierra Leone 13. Tanzania 14. Uganda 15. Chad 16. Equatorial Guinea 17. Ethiopia

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Yellow fever is an acute disease of viral etiology with natural focality, transmitted by mosquitoes, and characterized by severe intoxication, hemorrhagic manifestations and damage to life-supporting human organs - the liver, kidneys. The name “yellow” is associated with the frequent development in patients of such a symptom as jaundice.

Most cases of yellow fever are recorded in countries with tropical and subtropical climates. There are two types of yellow fever:
1) Endemic (common in rural areas or jungles),
2) Epidemic (predominantly distributed in cities, anthroponotic).

Yellow fever is a particularly dangerous infection (EDI) and is classified as a quarantine disease subject to international registration. Travel to yellow fever-endemic countries requires an international certificate of vaccination against this infection.

International certificate

Natural foci of yellow fever are located in the tropical zones of South America and Africa. According to WHO, 45 countries in Africa and 13 countries in South and Central America are currently endemic, examples of which are: Congo, Sudan, Senegal, Bolivia, Peru, Brazil, Mexico, Cameroon, Nigeria, Zambia, Uganda, Somalia and others.

The disease is dangerous due to the development of outbreaks among the population. For example, in 2012, an outbreak in Sudan sickened 850 people, 171 of whom died. Outbreaks occur annually in endemic countries. The only preventive measure is vaccination, which reduces the incidence of disease in the population.

The causative agent of yellow fever

Yellow fever is caused by an arbovirus from the Flaviviridae family of the Flavivirus genus. The virus genome contains RNA. Strains from different places in Africa and America are not genetically homogeneous.

The virus is not very stable in the external environment and dies quickly when exposed to high temperature and conventional disinfectants. The virus persists for a long time in the frozen state and when dried.

The yellow fever virus is classified as pathogenicity group 1 (all types of work with such viruses are carried out in the most isolated laboratories). The virus can be isolated from the blood of a yellow fever patient during the first three days of illness using white mice and monkeys, and also from the liver and spleen in sectional (fatal) cases.

Causes of yellow fever

The main source and reservoir of infection in the jungle form of yellow fever is wild animals (monkeys, possums, marsupials, rodents and others), and in the urban form it is humans.

The infectious period of the source in animals cannot be determined, but in humans this period begins shortly before the appearance of clinical signs of the disease and lasts for 3-4 days.

The yellow fever virus is transmitted by mosquitoes, both domestic and wild. Mosquitoes become infectious 9 - 12 days after blood sucking at ambient temperatures up to 25 ° C, after 7 days at 30 degrees, after 4 days at 37 degrees, at temperatures below 18 degrees the mosquito loses the ability to transmit the virus. Accordingly, the hotter the climate, the faster the mosquito becomes infectious. In the absence of mosquitoes, a sick person is not infectious to others. The incidence increases after the rainy season when the mosquito population increases.

The mechanism of transmission of the pathogen is transmissible, the carriers in urban areas are Aedes aegypti mosquitoes, and in the jungle there are some other representatives of this genus. Contact and parenteral transmission routes (through infected blood) are possible. Cases of laboratory contamination have been reported.

The natural susceptibility of people is high; both children and adults get sick. In endemic countries, the local population has latent (asymptomatic) immunization with small doses of the virus, they do not get sick, and immunity develops.

After an infection, in case of a favorable outcome, stable immunity develops (up to 6 years or more).

How does the disease develop?

When bitten, the virus enters through the lymphatic system into lymph nodes close to the site of the bite (regional), in which it multiplies (in humans, the incubation period is 3-6 days).

Then the virus spreads hematogenously (through the blood) throughout the body and causes damage to the liver, spleen, kidneys, bone marrow and brain (the patient has a viremia period of 3-5 days). Noteworthy is the virus’s favorite damage to the blood vessels of these organs, the result of which will be an increase in the permeability of the capillary bed vessels. Along with this, cell damage develops: degeneration and necrosis of liver and kidney cells. Internal hemorrhagic syndrome (bleeding into internal organs - spleen, heart, brain, intestines, lungs) is unconditional and severe. It is obvious that such severe lesions are often incompatible with life.

Symptoms of yellow fever

The incubation period (from the moment of infection to the appearance of symptoms of the disease) lasts on average from 3 to 6 days. The typical course of yellow fever has a peculiar “two-wave” character with 3 periods:

1) initial;
2) period of remission (improvement);
3) period of venous stasis (sharp deterioration).

There are also several forms of severity: light, moderate, heavy and lightning.

1. Initial (febrile) period lasts 3-4 days. The disease begins acutely and is characterized by a sharp rise in temperature with a maximum level of up to 40° already on the first day of illness. Patients are worried about chills, severe headache, muscle pain in the back and limbs, vomiting, often repeated, thirst, and general weakness. The pulse is increased to 130 per minute, blood pressure is normal, heart sounds are muffled. Patients with yellow fever in the initial period are characterized by the so-called “amaryl mask” (redness of the face, neck, conjunctiva and sclera of the eyes - vascular injection, swelling of the eyelids, puffy face, swollen lips).

Patients are irritated by bright lights and have sleep disturbances. Patients are irritable, the skin is hot and dry. Often there is no criticism of one’s condition, but there is fear and euphoria. The liver and spleen are enlarged and painful on palpation. In the peripheral blood there is neutropenia and lymphopenia, ESR is not increased. There is proteinuria in the urine.

On the 3rd day of illness, jaundice appears (first the sclera of the eyes turn yellow, then the mucous membranes of the mouth, eyelids and skin).

Hemodynamic disturbances quickly develop (blood pressure drops, the skin becomes bluish). The patient gets worse: the initial manifestations of hemorrhagic syndrome appear - bleeding gums, nosebleeds, blood in the stool and vomit. The patient's pulse slows down greatly. In severe cases of the disease, the patient may die during this period.

2. With a milder course of the disease, period of remission(4-5 days from the onset of the disease): the temperature decreases, the condition improves, vomiting stops. This period can last from several hours to a day and with a mild course the patient gets better. More often, severe forms are observed and the 3rd period begins.

3. The period of venous stagnation (lasts 3-4 days). The temperature rises again, jaundice intensifies, as well as hemorrhagic manifestations become more pronounced: nasal, uterine, gastrointestinal bleeding, large hemorrhages appear on the skin.

Acute renal failure develops rapidly with severe albuminuria (protein in the urine), oliguria (decreased diuresis), and possible anuria (lack of diuresis). Blood pressure drops, heart sounds are muffled, pulse up to 40 beats per minute, extrasystole, collapse is possible. The size of the liver is increased, becomes dense, sharply painful on palpation due to stretching of the liver capsule. During a biochemical examination of blood: indicators of direct and indirect bilirubin, ALT increase, the content of leukocytes decreases to 1.5-2.5 thousand in 1 μl, neutropenia and lymphopenia are noted. Blood clotting slows down and ESR increases. These changes are most typical for days 6-7 of illness. This is a critical period for the patient, the amount of protein in the urine increases to 10 g/l, granular and hyaline casts appear.

Death occurs in 50% of cases, more often from acute renal failure with the development of uremic coma (cerebral edema, loss of consciousness) and toxic encephalitis, less often from hepatic coma or cardiovascular failure (myocarditis).

With a favorable course of the disease, from the 8th-9th day of illness, the general condition gradually improves, a period of recovery (convalescence) begins, and laboratory parameters normalize. A slight weakness as a residual phenomenon persists for a week.

Complications of yellow fever

Complications of yellow fever are: pneumonia, kidney abscess, encephalitis, there may be gangrene of soft tissues, and death is possible.

When should you see a doctor?

If you are in an endemic country or have recently arrived (3-6 days) from it, then the appearance of the first symptom - high temperature on the first day of illness should force you to see a doctor. No self-medication is allowed! Urgent hospitalization only!

Diagnosis of yellow fever

A preliminary diagnosis is made based on:

1) Arrival or stay in an endemic region (countries of Africa and South America) - tropics and subtropics;
2) Symptoms of the disease (“saddle-shaped” or “two-wave” temperature curve, hemorrhagic syndrome, jaundice, damage to the kidneys, liver and spleen);
3) Laboratory data: (in biochemistry - increase in bilirubin, ALT, AST, urea, creatinine, in a general blood test - inhibition of hematopoietic sprouts - decrease in leukocytes, neutrophils, lymphocytes, decrease in platelets, acceleration of ESR, in urine - protein, casts, red blood cells ) And so on.

The final diagnosis is confirmed by specific laboratory data when
examination of the blood of a patient suspected of yellow fever, taken before the 3rd-4th day of illness.
1) Biological method (by intracerebral infection of newborn or young white mice).
2) Express diagnostics based on antigen indication - carried out using the ELISA method, the result is in 3 hours.
3) From serological reactions, RN, RSK, RTGA, RNGA are used, they are performed with paired sera taken at the end of the first week of the disease and after 2-3 days.
4) In case of death, the liver is histologically examined, where foci of submassive and massive necrosis of the hepatic lobules and acidophilic Councilman's bodies are detected.

Yellow fever is differentiated from influenza, viral hepatitis, tropical malaria, the icteric form of leptospirosis, Dengue fever, tick-borne relapsing fever, Crimean hemorrhagic fever, Lassa, Ebola, and Marburg hemorrhagic fevers.

Treatment of yellow fever

1. Organizational and routine measures. Hospitalization of all patients in a hospital and strict bed rest! Violation of this clause may cost a person his life. Dairy-vegetable diet with a complex of vitamins (C, B).
2. There is no etiotropic (antiviral) treatment.
3. Pathogenetic and symptomatic treatment:
- detoxification (glucose-saline solutions, albumin solutions);
- prevention and treatment of hemorrhagic syndrome (prednisolone, aminocaproic acid, colloidal solutions, blood transfusion if indicated);
- for renal failure (dehydration, stimulation of diuresis, hemodialysis if indicated);
- in case of liver damage (detoxification of the body - hepasol, hepatoprotectors, glucose, etc.)
- when secondary bacterial infections occur, antibiotics are prescribed.

Prevention of yellow fever

Preventive measures are aimed at preventing the introduction of infection from abroad.

1) They destroy mosquitoes and their breeding sites, protect premises and use from them
personal protective equipment.
2) Single live immunization is used as a means of immunoprophylaxis.
weakened vaccine, mainly from strain 17-D (0.5 ml diluted 1:10 subcutaneously), persons aged 9 months. and older, living in endemic areas or intending to visit them, with revaccination after 10 years. Immunity is developed from the 10th day after vaccination and from the 1st day after revaccination. Russia uses one Russian-made vaccine that meets WHO requirements. The Stamaril Pasteur vaccine produced by Aventis Pasteur (France) is prescribed abroad.
All vaccinated persons are issued an international certificate of vaccination or revaccination against yellow fever, which is individual and completed in English and French. The certificate becomes valid from the 10th day after vaccination and for 10 years.

Vaccination is recommended for people traveling to the following countries: Angola, Argentina, Benin, Guinea-Bissau, Bolivia, Brazil, Burkina Faso, Burundi, Venezuela, Gabon, Gambia, Ghana, Guinea, Guana, Democratic Republic of the Congo, Cameroon, Kenya, Colombia, Congo , Ivory Coast, Liberia, Mauritania, Mali, Niger, Nigeria, Panama, Paraguay, Peru, Rwanda, Senegal, Sudan, Suriname, Sierra Leone, Togo, Uganda, French Guiana, Central African Republic, Chad, Ecuador, Equatorial Guinea, Ethiopia, South Sudan.

Infectious disease doctor N.I. Bykova

• Yellow fever is an acute viral hemorrhagic disease transmitted by infected mosquitoes. It is called “yellow” because some patients develop jaundice.
• Symptoms: high fever, headache, jaundice, myalgia, nausea, vomiting and fatigue.
• A small proportion of patients infected with the virus develop severe symptoms, and about half of them die within 7 to 10 days.
• The virus is endemic in tropical areas of Africa and Central and South America.
• Large epidemics of yellow fever occur when infected people introduce the virus into densely populated areas with high mosquito population densities and little or no immunity to the disease in the majority of the population due to lack of vaccination. Under such conditions, human-to-human transmission of the virus by infected mosquitoes begins.
• Yellow fever can be prevented with extremely effective vaccinations. The vaccine is safe and affordable. One dose of yellow fever vaccine is sufficient to provide lifelong immunity against yellow fever without the need for booster vaccination. The yellow fever vaccine is safe and affordable, providing effective immunity against yellow fever in 80-100% of vaccinated individuals within 10 days and in more than 99% of individuals within 30 days.
• Providing good supportive care in hospitals improves survival rates. There are currently no antiviral drugs against yellow fever.
• The End Yellow Fever Epidemic (EYE) strategy, launched in 2017, is an unprecedented initiative involving more than 50 partners.
• The EYE Partnership supports 40 at-risk countries in Africa and the Americas to prevent, detect and respond to outbreaks and suspected cases of yellow fever. The partnership's goal is to protect vulnerable populations, prevent international spread of the disease, and quickly eliminate outbreaks. By 2026, more than a billion people are expected to be protected from the disease.

Signs and symptoms

The incubation period of the virus in the human body is 3-6 days. In many cases, the disease is asymptomatic. When symptoms appear, the most common are fever, muscle pain with severe back pain, headache, loss of appetite and nausea or vomiting. In most cases, symptoms disappear within 3-4 days.

However, in a small proportion of patients, a second, more severe phase of the disease occurs within 24 hours after the initial symptoms disappear. The temperature rises again and a number of body systems are damaged, usually the liver and kidneys. This phase is often characterized by jaundice (yellowing of the skin and eyeballs, hence the name of the disease - “yellow fever”), dark urine, abdominal pain and vomiting. There may be bleeding from the mouth, nose, or stomach bleeding. Half of the patients whose disease enters the toxic phase die within 7-10 days.

Diagnostics

Yellow fever is difficult to diagnose, especially in the early stages. Severe forms of the disease can be confused with severe malaria, leptospirosis, viral hepatitis (especially fulminant), other hemorrhagic fevers, infection with other flaviviruses (for example, dengue hemorrhagic fever) and poisoning.

In some cases, a blood test (RT-PCR) can detect the virus in the early stages of the disease. In the later stages of the disease, testing for the presence of antibodies is necessary (enzyme immunoassay and plaque neutralization test).

At-risk groups

Forty-seven countries—in Africa (34) and Central and South America (13)—are either endemic or have regions where yellow fever is endemic. Modeling based on data from African countries estimated the burden of yellow fever in 2013 to be 84,000–170,000 severe cases and 29,000–60,000 deaths.

Occasionally, travelers to countries where yellow fever is endemic may introduce the disease to countries where it is not present. To prevent imported infections, many countries require proof of yellow fever vaccination when issuing visas, especially if the person lives in or has visited an endemic area.

In the past (17th to 19th centuries), yellow fever spread to North America and Europe, causing major outbreaks of the disease, damaging the economies of countries, disrupting their development and, in some cases, leading to the death of large numbers of people.

Transmission of infection

Yellow fever virus is an arbovirus of the genus flavivirus, and the main vectors are mosquitoes of the Aedes and Haemogogus species. The habitats of these mosquito species can vary: some breed either near homes (domestic), or in the jungle (wild), or in both habitats (semi-domestic). There are three types of transmission cycles.

• Forest yellow fever: In tropical rainforests, monkeys, which are the main reservoir of infection, become infected by the bite of wild Aedes and Haemogogus mosquitoes and transmit the virus to other monkeys. Periodically, infected mosquitoes bite people working or staying in forests, after which people develop yellow fever.
• Intermediate yellow fever: in this case, semi-domestic mosquitoes (those that breed both in the wild and near homes) infect both monkeys and humans. More frequent contact between people and infected mosquitoes leads to more frequent transmission, and outbreaks can occur simultaneously in many isolated villages in separate areas. This is the most common type of outbreak in Africa.
• Urban yellow fever: Major epidemics occur when infected people introduce the virus into densely populated areas with high population densities of Aedes and Haemogogus mosquitoes and little or no immunity to the disease in the majority of the population due to lack of vaccination or previous yellow fever. Under these conditions, infected mosquitoes transmit the virus from person to person.

Treatment

Proper and timely supportive care in hospitals improves patient survival rates. There is currently no antiviral drug for yellow fever, but providing treatment for dehydration, liver or kidney failure, and fever can reduce the likelihood of an adverse outcome. Associated bacterial infections can be treated with antibiotics.

Prevention

1. Vaccination

Vaccination is the main way to prevent yellow fever.

The yellow fever vaccine is safe and inexpensive. Moreover, one dose of the vaccine is sufficient to form lifelong immunity without the need for revaccination.

A number of strategies are used to prevent yellow fever and its spread: routine immunization of infants; conducting mass vaccination campaigns to expand coverage in countries at risk of disease outbreaks; vaccination of travelers to areas where yellow fever is endemic.

In high-risk areas characterized by low vaccination coverage, the most important condition for preventing epidemics is the timely detection and suppression of disease outbreaks through mass vaccination of the population. At the same time, in order to prevent further spread of the disease in the region where the outbreak is recorded, it is important to ensure high immunization coverage of the population at risk (at least 80%).

In rare cases, serious side effects of the yellow fever vaccine have been reported. The incidence of these serious “adverse events following immunization” (AEFIs), where liver, kidney and nervous system damage occurs after vaccine administration, ranges from 0.09 to 0.4 per 10,000 vaccine doses in populations not exposed to the virus.

The risk of AEFI is higher in persons over 60 years of age, patients with severe immunodeficiency due to symptomatic HIV/AIDS or other factors, and persons with thymus gland disorders. Vaccination of people over 60 years of age should be carried out after a careful assessment of the potential risks and benefits of immunization.

As a rule, people who are not eligible for vaccination include:

• infants under 9 months;
• pregnant women (except in cases of yellow fever outbreak and high risk of infection);
• persons with severe forms of egg white allergy;
• persons with severe immunodeficiency due to symptomatic HIV/AIDS or other factors, as well as persons with disorders of the thymus gland.

Under the International Health Regulations (IHR), countries have the right to require travelers to provide proof of vaccination against yellow fever. If there are medical contraindications to vaccination, you must provide an appropriate certificate from the competent authorities. The IHR is a legally binding framework designed to prevent the spread of infectious diseases and other public health threats. The requirement for travelers to provide proof of vaccination is left to the discretion of each participating State and is not currently practiced by all countries.

2. Control of mosquitoes that transmit the disease

The risk of yellow fever transmission in urban areas can be reduced by eliminating mosquito breeding sites, including - treating tanks and other objects with standing water with larvicides.

Both surveillance and vector control are elements of strategies for the prevention and control of diseases caused by insect vectors, including those used to prevent disease transmission during epidemics. In the case of yellow fever, epidemiological surveillance of mosquitoes of the species Aedes aegypti and other types Aedes helps to obtain information about the risk of outbreaks in cities.

Based on information about the distribution of mosquito species across the country, it is possible to identify areas where human disease surveillance and testing need to be strengthened, and vector control activities need to be developed. Currently, the arsenal of safe, effective and cost-effective insecticides that can be used against adult mosquitoes is limited. This is mainly due to the resistance of these mosquito species to common insecticides, as well as the abandonment or recall of certain pesticides due to safety reasons or high re-registration costs.

In the past, mosquito control campaigns have eradicated Aedes aegypti, the vector of yellow fever, from urban areas in much of Central and South America. However, Aedes aegypti has re-introduced urban areas in the region, again creating a high risk of urban transmission. Mosquito control programs targeting wild mosquito populations in forested areas are not suitable for preventing the transmission of sylvatic yellow fever.

To avoid mosquito bites, it is recommended to use personal protective equipment such as covered clothing and repellents. The use of mosquito nets on beds has limited effectiveness because mosquitoes Aedes active during the daytime.

3. Epidemic preparedness and response

Rapid detection of yellow fever and rapid response through the initiation of emergency vaccination campaigns are critical tools for controlling outbreaks. However, there is a problem of under-reporting of cases, with the actual number of cases estimated to be 10 to 250 times higher than today's official statistics.

WHO recommends that every country at risk of a yellow fever epidemic have at least one national laboratory that can perform basic blood tests for yellow fever. One case in an unvaccinated population is already being considered an outbreak of yellow fever. In any case, all laboratory-confirmed cases should be subject to thorough investigation. Investigation teams must assess the characteristics of the outbreak and implement both immediate and long-term response measures.

WHO activities

In 2016, two linked outbreaks of yellow fever in the cities of Luanda (Angola) and Kinshasa (Democratic Republic of Congo) resulted in the disease spreading widely from Angola throughout the world, including China. This fact confirms that yellow fever is a serious global threat that requires a new strategic approach.

The Ending Yellow Fever Epidemic (EYE) strategy was developed in response to the growing threat of urban yellow fever outbreaks and the spread of the disease throughout the world. The strategy is led by WHO, UNICEF and GAVI (Global Alliance for Vaccines and Immunization) and covers 40 countries. Over 50 partners are working on its implementation.

The EYE global strategy is designed to solve three strategic objectives:

1. protection of the population at risk
2. preventing the spread of yellow fever throughout the world
3. quickly eliminate outbreaks

To successfully solve these problems, five components are required:

1. accessible vaccines and a stable vaccine market
2. strong political will at the international and regional levels, as well as at the level of individual countries
3. high-level decision-making based on long-term partnership
4. synergy with other health programs and sectors
5. Research and development to improve tools and practices.

The EYE strategy is complex, multi-component, combining the efforts of many partners. In addition to recommended vaccination activities, the strategy calls for the creation of urban sustainability centres, urban outbreak preparedness planning and more consistent application of the International Health Regulations (2005).

EYE Strategy partners are supporting countries at high and moderate risk of yellow fever in Africa and the Americas by strengthening their surveillance and laboratory capacity to respond to yellow fever outbreaks and cases. In addition, EYE strategy partners support the deployment and sustainable implementation of routine immunization programs and vaccination campaigns (preventive, proactive and reactive) anywhere in the world and at any time when needed.