What Is Yellow Fever?


The yellow fever virus, a flavivirus, is transmitted by mosquitoes and is endemic in tropical South America and sub-Saharan Africa. The symptoms can consist of sudden fever onset, relative bradycardia, headache and, in severe cases, jaundice, hemorrhages and multiple organ failure. The diagnosis is made by a virus cell culture, reverse transcription and serological tests. Treatment is supportive. For prevention are vaccination and control of mosquitoes available.

(See also Overview of infections by Arbovirus, Arena virus and filovirus.)

The yellow fever virus, a flavivirus, is transmitted by mosquitoes and is endemic in tropical South America and sub-Saharan Africa. The complaints can u. a. consist of sudden fever onset, relative bradycardia, headache and, in severe cases, jaundice,

hemorrhages and multiple organ failure. The diagnosis is made by a virus cell culture, reverse transcription and serological tests. Treatment is supportive. For prevention are vaccination and control of mosquitoes available. (See also Overview of infections by Arbovirus, Arena virus and filovirus.) In urban yellow fever virus is transmitted by the bite of an Aedes aegypti mosquito, which has about 2 weeks previously infected by a blood meal to a person with viremia. In Jungle (sylvatischem) Yellow fever is the virus through Haemagogus – transfer and other forest mosquitoes which acquire the virus from wild primates. The incidence is in South America during the month of maximum rainy season, humidity and temperature highest in Africa during the late rainy season and early dry season.

Symptoms and Signs

The infection may be asymptomatic (5-50% of cases) or symptomatic run up to a hemorrhagic fever with a mortality of 50%. The incubation period is 3-6 days. The onset is sudden, with fever of 39-40 ° C, chills, headache, dizziness and myalgia. The pulse rate is usually increased initially, but then slowed down from the 2nd day depending on the degree of fever (Faget’s sign). The face is flushed and the conjunctiva of the eyes are injected. There is often nausea, vomiting, constipation, severe exhaustion, restlessness and irritability. With a slight disease can occur after 1-3 days for recovery. In moderate or severe cases the fever but drops suddenly 2-5 days after onset and occurs over several hours or days to remission. The fever then recurs, however, the pulse rate remains low. After 5 days of illness, there is often an accompanying jaundice ( “yellow fever”), extreme albuminuria and abdominal rigidity with hematemesis.

There may be oliguria , petechiae, mucosal hemorrhages, confusion and apathy. The disease can> 1 week continue with rapid recovery without sequelae. In the most severe form (called malignant yellow fever) it comes to terminal delirium, intractable hiccups, seizures, coma, and multiple organ failure. In the recovery phase secondary bacterial infections, particularly pneumonia, may occur. Diagnosis Viral culture, reverse transcription-PCR (RT-PCR) or serological testing the suspected yellow fever, patients in endemic areas if they suddenly develop a fever with relative bradycardia and jaundice; mild cases often miss the diagnosis. It should made a blood count, liver parameters and coagulation values ??determined and viral cell culture and serological tests are carried out. There is often a leukopenia with a relative neutropenia, as well as to a thrombocytopenia, prolonged clotting time and increased prothrombin time (PT). The bilirubin and aminotransferase levels may be elevated acutely and over several weeks. Albuminuria, which occurs in 90% of patients, can reach up to 20 g / l; it is helpful to differentiate yellow fever from a hepatitis. In malignant yellow fever, it can präfinal lead to hypoglycaemia and hyperkalemia.

The clinical diagnosis is confirmed by virus cell culture, serology, RT-PCR or by the detection of a characteristic autopsy central hepatocytic necrosis. Due to the risk of haemorrhage fine needle punctures the liver during the disease are contraindicated. Therapy Supportive treatment It die up to 10% of patients in whom the disease is severe enough that a diagnosis is made. Treatment is mainly supportive. Bleeding can be treated with Vitamin K A H2 blockers or proton pump inhibitors and sucralfate may be useful as prophylaxis for GI bleeding and are used in all patients who are so ill that hospitalization is necessary. Suspected and confirmed cases require quarantine measures.

Prevention

Preventive measures include avoiding mosquito bites Vaccinations The most effective prevention method to prevent outbreaks is to reduce the number of mosquitoes and limiting mosquito bites through the use of diethyl toluamide (DEET), the use of mosquito nets and protective clothing. During outbreaks in the jungle, people should temporarily leave the area until the actual immunization and mosquito control. Rapid mass yellow fever vaccination of the population is used to control a current yellow fever outbreak by immunization. A single dose of the vaccine can provide lifelong immunity against yellow fever.

For travelers to endemic areas, an active immunization with the 17D strain an attenuated yellow fever vaccine is live (0.5 ml s.c. every 10 years) indexed and effectively to 95%. Although one  dose of yellow fever vaccine provides long-lasting protection, WHO and the Advisory Committee of the CDC on Immunization Practices do not  recommend implementing  booster dosages for most travelers every 10 years, is not known at all points of entry that this requirement was abolished; Thus, it is probably safer to get the booster and not to risk not being allowed to enter. In Germany, the vaccine must be administered only by authorized yellow fever vaccination centers (CDC: yellow fever vaccination). In the following cases, the vaccine is contraindicated: Pregnant infants <6 mo people with impaired immunity When children aged 6-8 months traveling in an endemic area cannot be avoided, should discuss parents vaccination with their doctor because the vaccine usually is available only from the age of 9 months. To prevent further mosquito-related transfers infected patients in rooms should be isolated that have tight-fitting window screens and were treated with insecticides.

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