Aleszu Bajak writes that researchers warn that a change of mosquito host could accelerate spread of chikungunya across the Americas.
In the past few months, passengers at North American airports have been warned that travel to the Caribbean might result in an unwanted souvenir. The first outbreak of chikungunya virus in the Western Hemisphere began in the French part of the Caribbean island of St Martin in December and has spread rapidly around the region, infecting more than 500,000 people.
Since then, at least 480 travellers have returned to the United States with the mosquito-borne disease, raising concerns that an insect biting one of those people would spark a US chikungunya outbreak. Yet so far, only four locally acquired cases have been confirmed in the country, all in southern Florida. The virus has gained more of a foothold in Central and South America: authorities have confirmed 174 cases of locally transmitted disease in El Salvador, Panama, Costa Rica, Venezuela and the Guianas (see ‘Tropical transfer’).
For now, the Caribbean strain of chikungunya does not seem likely to expand into the rest of the Western Hemisphere, mostly because it is spread by the tropical mosquito Aedes aegypti. However, several major chikungunya outbreaks have been fuelled by a specific mutation of the virus that makes it more suited to transmission by a different species of mosquito — a scenario analysed by Carrie Manore, a mathematical epidemiologist at Tulane University in New Orleans, Louisiana, and her colleagues. They report that genetic changes in the virus could propel chikungunya deep into North and South America (C. A. Manore et al. J. Theor. Biol. 356, 174–191; 2014). The insect that could cause the damage is the Asian tiger mosquito (Aedes albopictus), which has been expanding worldwide for the past two decades and taking diseases such as chikungunya and dengue with it (see Nature 489,187–188; 2012).
The Caribbean is fertile ground for the spread of the disease, no matter which mosquito is spreading it. In temperate regions, winter weather kills A. aegypti mosquitoes and acts as a natural brake on the spread of the diseases they carry. But in the Caribbean, A. aegypti can survive year-round, and serves as an outstanding host vector for diseases, says Sylvain Aldighieri, a physician at the Pan American Health Organization in Washington DC who has helped to track the current outbreak. [. . .]
For full report, see http://www.nature.com/news/us-assesses-virus-of-the-caribbean-1.15710