YELLOW FEVER

DEFINITION: yellow fever is a viral disease caused by the yellow fever virus which is carried by mosquitoes. It is endemic in 33 countries in Africa and 11 countries in South America.

HOW YELLOW FEVER IS SPREAD

The yellow fever virus can be transmitted by mosquitoes which feed on infected animals in forests, then pass the infection when the same mosquitoes feed on humans travelling through the forest. The greatest risk of an epidemic occurs when an infected humans return to urban areas and are fed on by the domestic vector mosquito Aedus aegypti, which than transmit the virus to other humans.

SIGN AND SYMPTOMS OF YELLOW FEVER

The illness may be so mild that it is not noticed or diagnosed. Three to six days after a person is infected, he or she suddenly develops fever, chills, headache, backache, general muscle pain, upset stomach and vomiting. As the disease progresses, the person becomes slow and weak. There may be bleeding from the gums and blood in the urine. Jaundice (yellowing in the white part of the eyes or yellowing of the skin and palms) and black vomiting may also occur.

The diagnosis of yellow fever is difficult to make because its signs and symptoms are similar to other diseases such as hepatitis, malaria, dengue and typhoid fever. As a result, any person who develops jaundice within two weeks of the start of a fever should be considered to be a possible case of yellow fever. To confirm the diagnosis of yellow fever, a blood sample should be taken and sent to a laboratory for testing.

COMPLICATION OF YELLOW FEVER

If the illness is severe, the patient may experience convulsions or a coma. The disease usually lasts two weeks, after which the patient either recovers or dies. In areas where the disease is endemic mortality is about 5%. However, up to half of infected people may die during epidemic.

TREATMENT OF YELLOW FEVER

There is no specific treatment for yellow fever, supportive treatment is indicated. Dehydration and fever can be treatment with oral rehydration salts and medication. Any accompanying bacterial infection should be treated with an antibiotic. Intensive supportive care may improve the outcome for seriously ill patients.

PREVENTION OF YELLOW FEVER

Immunization is the single most important measure to control yellow fever. The main strategies to control yellow are based on a combination of immunization for protection against the disease and surveillance, and are outlined below.

Prevention

* Administering yellow fever vaccine as part of routine infant immunization.

* Preventing outbreaks in high-risk areas through mass campaign;

* Control of Aedes aeguptica in urban centres.

Both these strategies should ensure a minimum coverage of at least 80%.

Control

* Instituting a sensitive and reliable YF surveillance system including laboratory capacity to analyze samples and confirm suspected cases;

* Emergency response to outbreaks through mass campaigns.