GALVESTON, Texas What causes a virus to suddenly begin infecting large numbers of people?
Scientists have long known that the process they call "viral emergence" involves a wide variety of factors. Some are changes in the environment, either generated by natural causes or human activity. Others are internal, arising from accidental changes mutations in the virus' genetic code.
Studying such mutations in different strains of the chikungunya virus has helped University of Texas Medical Branch researchers solve one of the most puzzling mysteries of chikungunya's emergence in Asia. They describe their results in an article in the online "Early Edition" section of the Proceedings of the National Academy of Sciences.
Chikungunya, which originated in Africa, is carried by mosquitoes and causes intensely painful arthritis that can last for months or years. Thanks to a discovery made at UTMB, scientists know that the virus' rapid spread was launched by a single mutation in an African strain of the virus.
The alteration was so small a single amino acid change in one of the virus' exterior "envelope" proteins that a researcher compared it to "a single missing comma in a six-page short story." But this so-called "E1-A226V mutation" made it possible for the virus to efficiently infect Aedes albopictus, a species of mosquito found nearly worldwide.
The mutated strain of the virus took full advantage of its new host, infecting millions of people as it spread across India, Thailand and Malaysia. It even jumped to northern Italy, carried by an infected traveler, where it established itself in the local Aedes albopictus mosquito population.
This albopictus-adapted strain's success raised a fundamental question, for this was not chikungunya's first visit to Asia. Strains of the virus transmitted by another mosquito species, Aedes aegypti, have caused sporadic outbreaks there for nearly six decades. If the virus
|Contact: Jim Kelly|
University of Texas Medical Branch at Galveston