Yellow fever - Causes, symptoms and treatment. MF.
Yellow fever is an acute disease of the viral etiology with a natural focality, transmitted by mosquitoes, and is characterized by severe intoxication, hemorrhagic manifestations and damage to the life supportive organs of the human liver, kidneys. The name "yellow" is associated with frequent development in patients of such a symptom as jaundice.
Most of the cases of yellow fever are registered in countries with a tropical and subtropical climate. There are two types of yellow fever:
1) Endemic( distributed in rural areas or jungles),
2) Epidemic( predominant distribution in cities, anthroponous).
Yellow fever is a particularly dangerous infection( OOI), refers to quarantine diseases that are subject to international registration. Departure to the country's yellow endemic fever requires an international certificate of vaccination against this infection.
International certificate
Natural centers of yellow fever are located in tropical regions of South America and Africa. According to WHO, only 45 countries in Africa and 13 countries of South and Central America are now endemic, with examples being Congo, Sudan, Senegal, Bolivia, Peru, Brazil, Mexico, Cameroon, Nigeria, Zambia, Uganda, Somalia and others.
Endemic countries for yellow fever
Disease is dangerous due to the development of outbreaks among the population. For example, in 2012, during the outbreak in the Sudan, 850 patients were ill, 171 of whom were fatal. Outbreaks in endemic countries occur annually. The only preventive measure is vaccination, which reduces the incidence of the population.
Yellow fever causative agent
Yellow fever causes arbovirus from the Flaviviridae family of the Flavivirus family. The genome of the virus contains RNA.Strains from different parts of Africa and America are not genetically homogeneous.
Yellow fever virus
The virus in the external environment is not very stable, quickly dies when exposed to high temperatures and ordinary disinfection. The virus persists for a long time in the frozen state and during drying.
Yellow fever virus is classified as pathogenicity group 1( all types of work with such viruses are carried out in maximally isolated laboratories).The virus can be isolated from the blood of a patient with yellow fever during the first three days of the disease using white mice and monkeys, as well as from the liver and spleen in sectional( fatal) cases.
The causes of yellow fever
The main source and reservoir of infection in the jungle form of yellow fever are wild animals( monkeys, opossums, marsupials, rodents and others), and in urban form - a person.
The infectious source period in animals can not be determined; in humans, this period begins shortly before the appearance of clinical signs of the disease, lasts for 3-4 days.
The vectors of the yellow fever virus are mosquitoes, both domestic and wild. Mosquitoes become infectious 9 to 12 days after the bloodsucking at ambient temperature to 25 ° C, after 7 days at 30 degrees, after 4 days at 37 degrees, at a temperature 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 contagious to others. The incidence increases after the rainy season, when the mosquito population increases.
The mechanism of transmission of the pathogen is transmissible, carriers in urban foci are mosquitoes Aеdes aegypti, in the jungle some other representatives of this genus. Possible contact and parenteral transmission routes( through infected blood).There were registered cases of laboratory infection.
Yellow fever transmission
The natural susceptibility of people is high, both children and adults suffer. In endemic countries, the local population has latent( asymptomatic) immunization with small doses of the virus, they do not fall ill, and immunity develops.
After the transferred infection in case of a favorable outcome, a stable immunity develops( up to 6 years and more).
How does the disease develop?
When bitten, the virus passes through the lymphatic system into the lymph nodes close to the site of the bite( regional), in which its reproduction occurs( in humans, the incubation period is 3-6 days).
Transmissible pathway of infection with yellow fever
Then the virus hematogenously( through the blood) spreads throughout the body and causes damage to the liver, spleen, kidneys, bone and brain( in the patient the period of viremia is 3-5 days).Attention is drawn to the favorite defeat of the vascular virus of these organs, the result of which will be an increase in the permeability of the vessels of the capillary bed. Along with this, cell damage develops: dystrophy and necrosis of liver cells, kidneys. Unconditional and severe is the internal hemorrhagic syndrome( hemorrhages in internal organs - the spleen, heart, brain, intestines, lungs).Obviously, such heavy defeats are often incompatible with life.
Symptoms of yellow fever
The incubation period( from the moment of infection to the onset of symptoms of the disease) lasts from 3 to 6 days on average. The typical course of yellow fever has a peculiar "two-wave" character with 3 periods:
1) initial;
2) the period of remission( improvement);
3) the period of venous stasis( severe deterioration).
There are also several forms of severity: light, medium, heavy and lightning.
1. The initial( febrile) period of lasts 3-4 days. The disease begins sharply, characterized by a sharp rise in temperature with a maximum level of 40 ° on the first day of the disease. Patients are concerned about chills, severe headache, muscle pain in the back and limbs, vomiting, often repeated, thirst, general weakness. Pulse is increased to 130 per minute, normal blood pressure, heart sounds are muffled. For patients, yellow fever in the initial period is characterized by the so-called "amaryl mask"( red face, neck, conjunctiva and sclera of the eye - injection of vessels, eyelid swelling, puffy face, swollen lips).
Patients are irritated by bright light, disturbed by sleep disorders. Patients are irritable, the skin is hot, dry. Often there is no criticism for one's condition, but there is fright and euphoria. The liver and spleen are enlarged in size, painful on palpation. In peripheral blood - neutropenia and lymphopenia, ESR is not increased. In urine, proteinuria.
On the third day of the disease jaundice( first yellowing sclera of the eye, then the mucous membranes of the mouth, eyelids and skin).
Jaundice with yellow fever
Quickly attached hemodynamic disorders( blood pressure drops, the skin acquires a cyanotic shade).The patient becomes worse: there are initial manifestations of hemorrhagic syndrome - bleeding gums, nosebleeds, an admixture of blood in the stool and vomit. The patient is severely impaired by the pulse. In severe illness during this period, the patient may die.
2. If the disease progresses more easily comes remission period( 4-5 days after the onset of the disease): the temperature decreases, the condition improves, vomiting stops. Such a period can last from a few hours to a day and with a mild course of the patient recovers. More often, heavy forms are observed and the third period begins.
3. Period of venous congestion( lasts 3-4 days). The temperature rises again, jaundice increases, as well as hemorrhagic manifestations become more pronounced: nasal, uterine, gastrointestinal bleeding, large hemorrhages appear on the skin.
Yellow yellow fever
Acute renal failure develops rapidly with pronounced albuminuria( protein in the urine), oliguria( a decrease in diuresis), anuria is possible( no diuresis).Blood pressure drops, heart sounds are muffled, pulse up to 40 beats per minute, extrasystole, collapse is possible. The dimensions of the liver are increased, becoming dense, sharply painful during palpation due to the dilatation of the liver capsule. In the biochemical examination of the blood: the indices of direct and indirect bilirubin, ALT increase, the white blood cell count drops to 1.5-2.5 thousand in 1 μl, neutropenia and lymphopenia are noted. Slowing blood coagulability, increased ESR.These changes are most typical for the 6-7th day of the disease. This is a critical period for the patient, in the urine the amount of protein increases to 10 g / l, granular and hyaline cylinders appear.
Fatal outcome 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 insufficiency( myocarditis).
With a favorable course of the disease from the 8th to 9th day of the disease, the general condition gradually improves, a recovery period( reconvalescence) occurs, and laboratory parameters are normalized. A slight weakness in the form of a residual phenomenon persists for a week. Complications of yellow fever
Complications of yellow fever are: pneumonia, kidney abscess, encephalitis, can be gangrene of soft tissues, possible fatal outcome.
When should I 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 fever on the first day of the illness should make you seek medical attention. No self-medication is permissible! Only urgent hospitalization!
Diagnosis of yellow fever
Preliminary diagnosis is made on the basis of:
1) Arrivals or locations in the endemic region( countries of Africa and South America) - tropics and subtropics;
2) Symptoms of the disease( "saddle" 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 the general blood test - oppression of germs of hematopoiesis - decrease in leukocytes, neutrophils, lymphocytes, platelet count, acceleration of ESR, in urine - protein,erythrocytes) and so on.
Two-wave temperature curve with yellow fever
The final diagnosis is confirmed by specific laboratory data for the
blood test of a suspicious yellow fever patient taken prior to the 3rd-4th day of illness.
1) Biological method( by intracerebral infection of newborns or young white mice).
2) Express diagnostics based on antigen indication - carried out using the ELISA method, the result after 3 hours.
3) From the serological reactions use RN, RSK, RTGA, RNGA, put paired sera taken at the end of the first week of the disease and after 2-3 days.
4) In a lethal outcome, the liver is examined histologically, where foci of submissive and massive necrosis of the hepatic lobules and Kaunsilmena acidophilus bodies are detected.
Yellow fever is differentiated with influenza, viral hepatitis, tropical malaria, icteric leptospirosis, Dengue fever, tick-borne recurrent typhoid, Crimean haemorrhagic fever, with hemorrhagic fevers Lassa, Ebola, Marburg.
Treatment of yellow fever
1. Organizational-regime measures. Hospitalization of all patients in the hospital and strict bed rest! Violation of this item can cost a person's life. Milk-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, according to indications, blood transfusion);
- with renal failure( dehydration, stimulation of diuresis, according to indications of hemodialysis);
- with liver damage( detoxification of the body - hepasol, hepatoprotectors, glucose, etc.)
- with the layering of secondary bacterial infections prescribe antibiotics.
Prevention of yellow fever
Preventive measures are aimed at preventing the introduction of infection from abroad.
1) Carry out the destruction of mosquitoes and their breeding sites, the protection of their premises and the use of
personal protective equipment.
2) As a means of immunoprophylaxis, a single immunization of live
with a weakened vaccine is used, mainly from strain 17-D( 0.5 ml in 1:10 dilution subcutaneously), persons aged 9 months.and older, residing in endemic areas or intending to visit them, with a booster in 10 years. Immunity is produced from 10 days after vaccination and from 1 - after revaccination. In Russia, one vaccine of Russian production is used that meets WHO requirements. The vaccine "Stamaryl Pasteur" produced by "Aventis Paster"( France) is appointed abroad.
All vaccinated persons receive an international certificate of vaccination or revaccination against yellow fever, which is individual and is filled in English and French. The certificate becomes valid from the 10th day after the vaccination and for 10 years.
Vaccination is recommended for people traveling to countries: Angola, Argentina, Benin, Guinea-Bissau, Bolivia, Brazil, Burkina Faso, Burundi, Cameroon, Cambodia, Cameroon, Congo, Côte d'Ivoire, Democratic Republic of the Congo, Gabon, Congo, Côte d'Ivoire, Liberia, Mauritania, Mali, Niger, Nigeria, Panama, Paraguay, Peru, Rwanda, Senegal, Sudan, Suriname, Sri Lanka, Togo, Uganda, French Guiana, Central African Republic, Chad, Ecuador, Equatorial Guinea, Ethiopia, South Sudan.
The doctor infektsionist Bykova N.I.