Yellow fever

The virus originates from monkeys and some other jungle animals while infected mosquitoes can transmit the disease to humans. It occurs in parts of Africa and South America, usually due to human contact with natural infection centres in forests (sylvatic yellow fever) or in urban environments (urban yellow fever).

According to the World Health Organisation, around 200,000 people, mainly those in rainforests, get infected with yellow fever every year. Yellow fever does not exist in Slovenia nor in Europe.

Cause

The causative agent is the yellow fever virus. It belongs to the group of so-called flaviviruses.

Incubation period

The time from infection to disease onset is 3–6 days, and even 13 days.

Transmission

The yellow fever virus is transmitted from a reservoir (usually monkeys) to humans through the bite of an infected mosquito. In South America, the vector is the Aedes aegypti or Haemagogus mosquito, and in Africa, various Aedes mosquitoes.

Susceptibility to infection

Anyone who has not had yellow fever is susceptible to contracting the virus. Immunity is permanent after vaccination or after the infection.

The virus is present in the patient’s blood just before the onset of fever and for 3–5 day after the onset of illness. Mosquitoes infected with the yellow fever virus remain infectious for life.

Symptoms

The disease can be asymptomatic or severe, and deaths are not uncommon. In the severe form, jaundice, haemorrhage and renal impairment occur. Severe disease develops in 10% to 20% of patients. As many as 50% of patients die of liver or kidney failure on days 7 to 9 of the disease. Rarely, signs of cardiac and central nervous system involvement develop, with recovery lasting several weeks.

Treatment

There is no antiviral medicine to treat yellow fever. Patients’ symptoms are alleviated with symptomatic treatment and support for the organ systems.