A type of viral infection, yellow fever is associated with flu-like symptoms, including fever, as well as more serious effects on the liver. The virus is transmitted by infected mosquitoes, who pass the infection to humans upon biting them. Yellow fever has three distinct transmission cycles, which are jungle, savannah, and urban.
The urban transmission cycle of yellow fever refers to infections that occur in urban settings. In this case, insects that live in proximity to human habitats acquire the virus after biting an infected person. These infected mosquitoes can then bite other people, which causes the virus to spread further. In many cases, the infected person responsible for passing the virus to mosquitoes acquired yellow fever in the savannah or jungle.
The savannah refers to a grassy woodland area within Africa, and people who live and work in this area may experience what’s called the intermediate transmission cycle of yellow fever. With this transmission cycle, a mosquito may bite an infected person or monkey and transmit the virus to another human upon biting them.
There’s also a jungle transmission cycle, which is sometimes known as sylvatic. In this case, mosquitoes bite monkeys infected with yellow fever and pass the virus to humans who are in the jungle.
Understanding how yellow fever spreads is vital for managing rates of infection. For example, individuals who visit jungle or savannah areas can take certain precautions to prevent infection. People living or working in high-risk areas are encouraged to get vaccinated, which can establish lifelong immunity after one dose of medication. Other preventative measures include:
Yellow fever can be life-threatening for some people, so preventative measures are key in reducing rates of infection and halting the spread of the virus.