The number of cases of chikungunya in the US has increased dramatically over the last two years. The disease occurs regularly in Africa, Asia and the Indian subcontinent. In recent decades travel and the spread of the mosquito vectors for chikungunya has increased the virus' range to include much or Europe. Despite ongoing control efforts, it has also been identified in several countries in the Caribbean and South America, and now in the US. Its spread, however, is difficult to track, particularly in South America. Chikungunya causes symptoms similar to dengue, another mosquito transmitted virus, which is common in Central and South America. Yet, unlike dengue --- for which primates are the only hosts --- cattle, rodents, birds and primates can all be reservoirs for chikungunya.
As a result, controlling chikungunya is more complex than controlling diseases such as dengue. While it is possible to increase the control of infected humans and livestock (although these measures are in no way foolproof), control of other hosts is difficult. In addition, over the last several decades, vector control efforts have proven ineffective. Thus, the most effective response remains prevention --- avoiding being bitten by infected mosquitos.
Yet, with new, locally acquired cases emerging in the US, hikungunya, it will be interesting to see if the international response changes. Given that winter generally slows mosquito activity in much of the US, and chikungunya generally doesn't kill patients, my guess is that the response will remain largely fragmented and domestic. If, however, Puerto Rico becomes the 51st state, the response to chikungunya by US officials might change dramatically. Puerto Rico has experienced a growing number of locally acquired cases in the last year after chikungunya was imported via tourism and vector movement. If Puerto Rico becomes a US state, US health officials would likely have increased interest in an heightened international response to better control the movement of vectors and infected hosts.
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