The Aedes aegypti or Haemagogus mosquito species acquire the virus that causes yellow fever when they obtain a blood meal from a human or non-human primate which carries the infection. The mosquito which has the virus then bites another human or animal and transmits the virus responsible for yellow fever to them.
Transmission Cycles
These transmission cycles between humans and non-human primates take place in jungle or sylvatic regions, urban areas, and in intermediate or savannah settings. The intermediate or savannah cycle occurs only in Africa, and the other two happen in endemic regions of Latin America and Africa.
The jungle or sylvatic cycle involves mosquito species which are present there, and they acquire the virus from non-human primates such as monkeys. Humans, especially young men, acquire the infection in jungles because the mosquitoes bite them when they work in the logging business in these forests or visit there for other reasons.
In the intermediate or savannah regions of Africa, transmission of the virus may occur from monkey-to-human or human-to-human via the mosquito. Humans who live or work near jungles are especially likely to acquire yellow fever in this situation. Moreover, humans who work in the jungle or savannah areas bring the virus to urban areas, and the mosquito then spreads the infection to other humans there.
The three cycles, therefore, enable the virus which causes yellow fever to transmit from monkey- to-human or vice-versa, human-to-human, and monkey-to-monkey via the mosquito which acquires the microbe (Centers for Disease Control, 2011).
Community Prevention
Mosquito control programs will significantly reduce the spread of this disease, but it is not practical to implement those programs in jungle or sylvatic areas. Sylvatic areas have wild mosquitoes, and elimination of them would require quite a bit of insecticide application to the region.
There is much benefit, nevertheless, from routine infant immunization in accordance with guidelines of the World Health Organization and United States Centers for Disease Control. Mass vaccination campaigns in areas at risk for yellow fever are also effective, and travelers should take the vaccine whenever there is a medical indication for it. It is necessary to immunize 60 to 80 percent of the population at risk in order to develop sufficient herd immunity that will prevent an epidemic.
Sources
- Centers for Disease Control. (2011). Yellow fever. Retrieved February 11, 2012.
- World Health Organization. (2011). Yellow fever. Fact sheet. Retrieved February 11, 2012.
Disclaimer: The information contained in this article is for educational purposes only and should not be used for diagnosis or to guide treatment without the opinion of a health professional. Any reader who is concerned about his or her health should contact their physician for advice.
Michael Koger - Dr. Koger obtained his medical education at Meharry Medical College and specialized in Internal Medicine.
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