Cause of Yellow Fever
In humans, yellow fever is caused by a bite from a mosquito that is infected with the yellow fever virus. Mosquitoes become infected with the virus by feeding on an infected monkey or human. After a mosquito acquires yellow fever, it can inject the virus into the human when it bites to take blood for feeding.
The yellow fever virus is a flavivirus (virus transmitted by mosquitoes) found in certain parts of Africa and South America. In South America, sporadic infections occur almost exclusively in forestry and agricultural workers, due to occupational exposure in or near forests.
In Africa, the virus is transmitted in three geographic regions:
- The moist savanna zones of West and Central Africa during the rainy season (most common)
- Urban locations and villages in Africa
- In jungle regions (to a lesser extent).
The virus can infect humans, primates, and mosquitoes, along with other animals.
Mosquitoes become infected with yellow fever in one of two ways: either when they feed on infected monkeys or infected humans.
When a mosquito becomes infected, the virus circulates within its blood for several days. Infected mosquitoes can then transmit yellow fever to uninfected humans while biting to take blood. During blood feeding, the yellow fever virus may be injected into a human. The virus can then multiply in the person's blood system and begin to cause yellow fever symptoms.
In order to minimize the chance of becoming infected, it is important to learn prevention strategies for yellow fever.