What is yellow fever?

I need to know about the virus and how it can be prevented? Also what the treatment is and the effects and symptoms of it.

Yellow fever (also called yellow jack, black vomit or vomito *****, or sometimes American Plague) is an acute viral disease. It is an important cause of hemorrhagic illness in many African and South American countries despite existence of an effective vaccine. The yellow refers to the jaundice symptoms that affect some patients.

PREVENTION:
In 1937, Max Theiler, working at the Rockefeller Foundation, developed a vaccine for yellow fever that gives a ten-year or more immunity from the disease and effectively protects people traveling to affected areas, while at the same time being a means to control the disease. According to the travel clinic at the University of Utah Hospital, the vaccine presents a significantly increased risk of severe allergic reaction in adults aged 60 and older, with the risk increasing again after age 65, and again after age 70. The reaction is capable of producing multiple organ failure and should be evaluated carefully by a qualified health professional before being administered to the elderly.

Woodcutters working in tropical areas should be particularly targeted for vaccination. Insecticides, protective clothing, and screening of houses are helpful, but not always sufficient for mosquito control; people should always use an insecticide spray while in certain areas. In affected areas, mosquito control methods have proven effective in decreasing the number of cases.

Recent studies have noted the increase in the number of areas affected by mosquito-borne viral infections and have called for further research and funding for vaccines.


TREATMENT
There is no true cure for yellow fever, therefore vaccination is important. Treatment is symptomatic and supportive only. Fluid replacement, fighting hypotension and transfusion of blood derivates is generally needed only in severe cases. In cases that result in acute renal failure, dialysis may be necessary. A fever victim needs to get lots of rest, fresh air, and drink plenty of fluids.


SYMPTOMS
The virus remains silent in the body during an incubation period of three to six days. There are then two disease phases. While some infections have no symptoms the first, acute phase is normally characterized by fever, muscle pain (with prominent backache), headache, shivers, loss of appetite, and nausea or vomiting. The high fever is often paradoxically associated with a slow pulse (known as *****'s sign). After three or four days most patients improve and their symptoms disappear.

Fifteen percent of patients, however, enter a toxic phase within 24 hours. Fever reappears and several body systems are affected. The patient rapidly develops jaundice and complains of abdominal pain with vomiting. Bleeding can occur from the mouth, nose, eyes, and stomach. Once this happens, blood appears in the vomit and feces. Kidney function deteriorates; this can range from abnormal protein levels in the urine (proteinuria) to complete kidney failure with no urine production (anuria). Half of the patients in the "toxic phase" die within fourteen days. The remainder recover without significant organ damage.

Yellow fever is difficult to recognize, especially during the early stages. It can easily be confused with malaria, typhoid, rickettsial diseases, haemorrhagic viral fevers (e.g. Lassa), arboviral infections (e.g. dengue), leptospirosis, viral hepatitis and poisoning (e.g. carbon tetrachloride). A laboratory analysis is required to confirm a suspect case. Blood tests (serology assays) can detect yellow fever antibodies that are produced in response to the infection. Several other techniques are used to identify the virus itself in blood specimens or liver tissue collected after death. These tests require highly trained laboratory staff using specialized equipment and materials.