Yellow Fever

Yellow fever is caused by the Flavivirus genus. It has been recognized as far back as 400 years. Infection causes a wide spectrum of disease, from mild symptoms to severe illness and death. Yellow fever in urban and some rural areas is transmitted by the bite of infective Aedes aegypti mosquitoes and by other mosquitoes in the forests of south America. The mosquitoes bite during daylight hours.

Yellow fever is generally found in Central America and Central Africa.

Reservoir

In urban areas: Humans and Aedes aegypti mosquito.

Incubation Period

Incubation period: Usually 2 - 5 days.

Signs and Symptoms

Yellow fever is an acute viral disease of short duration with a wide variation in intensity.

• Headache
• Fever (mild or with chills and myalgia)
• The triad of jaundice, haemorrhage and severe albuminuria is present only in a small number of severe cases.

Malignant cases: Have three stages:

• Stage one: Fever, chills, backache, myalgia, nausea, vomiting and epistaxis with Fagets sign (relative bradycardia: high temperature, slow pulse) that appear on the second day. On the third day, the fever falls by crisis and patient enters remission.
• Stage two: Remission that may last several hours to several days but haemorrhages, anuria and delirium may occur without remission.
• Stage three: Development of the classic symptoms of jaundice and haemorrhagic manifestations (epistaxis, haematemesis, malaena and uterine bleeding) followed by albuminuria, coma and death two to three days later.

Diagnosis

It is diagnosed by:

• Serology: presence of IgM in early sera.
• Virus isolation by mice inoculation or cell culture.

Treatment

There are no medicines that are effective against this virus.

Serious cases of yellow fever always need hospital treatment. As there are no products that combat the virus itself, the doctor can only treat the symptoms. Dehydration is treated by administering intravenous fluids.

In mild cases, the pain may be relieved with simple painkillers.

Control and Prevention

In endemic areas, access of mosquitoes should be prevented (with mosquito nets and residual sprays).

All travellers to endemic areas should be immunised. A yellow fever vaccination certificate is valid for 10 years and begins 10 days after vaccination.