El Nino and climate change contributing factors in the dispersal of Zika virus in the Americas?
In their letter, Isaac I Bogoch and colleagues Jan 23, p 335) anticipated the international spread of Zika virus from Brazil through air traffi c. Permissive climatic conditions for Aedes mosquitoes might have contributed to the explosive spread of Zika virus in Brazil. In fact, the 2015 El Nino caused exceptional climatic conditions in northeastern South America during winter and spring in the southern hemisphere. According to the US National Oceanic and Atmospheric Administration, the temperatures over north and eastern South America were "record warmest" accompanied by a severe drought, throughout the second half of 2015. These extreme conditions might also be a manifestation of climate change that have contributed to the rapid dispersal of the Zika virus. A striking overlap emerges when regions with extreme climatic conditions in one month are juxtaposed to the geographic distribution of Zika virus in the subsequent month (appendix) Temperature is known to have a role in adult vector survival, viral replication, and infective periods. Elevated temperatures (within a temperature envelope) can expand the geographic vector range, decrease the extrinsic incubation period of the pathogen, and increase the female mosquito biting rate. Although precipitation provides essential habitat for larvae during the aquatic stages of the Aedes lifecycle, drought can indirectly expand the vector's range. In several locations (including northeastern Brazil) the risk of range expansion of Aedes aegypti is correlated with an increase in water storage in household containers during a persistent regional drought. Thus, the unique climatic conditions created during this severe El Nino event should be considered contributing factors in the dispersal of Zika virus in the Americas and should also be considered as the virus continues to spread.
The Lancet