Resistance To Yellow Fever

Mosquito Mouthparts

Mosquito Mouthparts

Annually, over a quarter million people (mostly in the tropics) are estimated to contract yellow fever and about 30,000 die, a rate slightly over 10 percent. This rate does not reflect the experience in all populations. The United States suffered from sporadic yellow fever outbreaks until the early 1900s, when methods of mosquito control and sanitation finally succeeded in disrupting major epidemics. In these epidemics, it was noted anecdotally that far more people of European ancestry died of yellow fever that those of some African ancestry. There was some suggestion that American Blacks were immune to the disease. Recently Blake and Garcia-Blanco* conducted a retrospective study of 6 yellow fever epidemics in the US with adequately detailed records of disease and mortality. They investigated several factors which might be correlated to mortality rates, including genetics. Interestingly, they found no difference in yellow fever incidence in the Caucasian and Non-Caucasion populations. Overall, 58.6% of Caucasions contracting yellow fever died; 8.4% of Non-caucasians contracting yellow fever died in the same epidemics, a rate that is 6.8 times less. Blake and Garcia-Blanco ruled out several factors that are not affecting differences in mortality including: differences in virus strain, acquired immunity, demographic differences in age or sex, and socioeconomic, environmental and cultural factors. All these factors have compelling evidence to negate their influence. This leaves genetic factors related to ability to fight off infection that are present in the Non-Caucasian population but not the Caucasian populations. If genetic differences are the key, future studies could lead to better understanding of how the body fights these disease and perhaps lead to new therapies.

*Lauren E. Blake & Mariano A. Garcia-Blanco. 2014. Human Genetic Variation and Yellow Fever Mortality during 19th Century U.S. Epidemics. 3 June 2014 mBio vol. 5 no. 3 e01253-14.
doi: 10.1128/mBio.01253-14

About jjneal

Jonathan Neal is an Associate Professor of Entomology at Purdue University and author of the textbook, Living With Insects (2010). This blog is a forum to communicate about the intersection of insects with people and policy. This is a personal blog. The opinions and materials posted here are those of the author and are in no way connected with those of my employer.
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