That insistent buzzing drone you hear? It’s the sound of our burgeoning mosquito problem and the nasty diseases that they carry wreaking havoc throughout the world. 2012 was a prodigious year for mosquito-borne arboviral diseases, with West Nile virus, Japanese encephalitis, malaria, dengue and yellow fever outbreaks and epidemics raging in the United States, the Sudan, Puerto Rico, Malaysia, Indonesia, India, Peru, Brazil and many other nations besides.
"Don't Mess With Texas," the road sign warning drivers throughout the State to not litter Texan roadways. This year, Texas had a more insidious mess on their hands. Image: Anne Ward. Click for source.
If you live in the US, you might know that this year the country suffered the largest outbreak of West Nile virus (WNV) since 2003. As of December 11th, infections with the virus have been reported in humans, birds and mosquitos in all of the lower 48 states. In humans, there have been a reported 5,387 cases of WNV disease with 2,734 or 51% of these cases classified as West Nile neuroinvasive disease (WNND), a severe manifestation of the infection resulting in encephalitis, chronic mental sequelae and occasionally death, and there have been 243 deaths; 80% of these cases have occurred in 13 states with a third of all cases reported in Texas (1).
Though it’s unknown why 2012 proved to be a particularly noxious and geographically expansive year for WNV in the States, there were several environmental factors that precipitated the outbreak’s emergence in Texas that may have influenced its severity. A short, mild winter at the tail end of 2011 may have allowed for greater numbers of mosquitos to survive the winter, an occurrence known as “overwintering”. In the spring and summer that followed, bouts of rain provided standing water for mosquito breeding and egg laying while droughts and higher than average temperatures may have also accelerated the replication of the WNV in birds and increased its transmissibility to mosquitoes, thereby augmenting its spread across the country (2)(3)(4)(5).
