An Introduction to the Transmission of Yellow Fever Virus
Yellow fever is spread by the bite of an infected mosquito. Yellow fever is not contagious, meaning that it is not passed directly from humans to other humans. Yellow fever is not spread through casual contact, such as touching or kissing a person with the virus.
Transmission of Yellow Fever Virus: Infected Mosquito
Transmission of the
yellow fever virus occurs in two main ways: urban (mosquito bites an infected human) and sylvatic (mosquito bites an infected monkey).
Urban
Urban yellow fever transmission occurs when a mosquito bites an infected human. Once infected, this mosquito can then bite and infect another human. An infected mosquito can continue to pass along the yellow fever virus for its entire life. Aedes aegypti is the type of mosquito that normally transmits this urban type of yellow fever. This type of yellow fever transmission can lead to an epidemic of yellow fever disease. For example, in Brazil in 1973, at least 21,000 individuals out of 1.5 million people became infected with the yellow fever virus.
Sylvatic
Sylvatic yellow fever transmission occurs when a mosquito bites an infected monkey. Once infected, this mosquito will usually bite other monkeys; however, in certain cases, this mosquito can bite humans. This type of yellow fever transmission is more sporadic and usually only occurs in people that work within tropical rain forests. In East Africa, this mode of yellow fever transmission occurs through the forest canopy mosquito, A. africanus, which seldom feeds on humans.
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