Friday, October 17, 2014

Mosquito Triad Plaguing Pacific

Dengue, Zika, Chikungunya. 

The names sound exotic and many probably have not even heard of the last two. They could be the names of primitive south American tribes, or names of towns in Papa New Guinea. What they actually are is a trimer of really dangerous, mosquito borne diseases. Frighteningly, there has been an increasingly high uptick of these viral disease in the Pacific since 2012. 

Mosquitoes are the vector of transmission ot humans for all 3 of these diseases, and all three can cause horrible complications including encephalitis and hemorrhagic fever syndromes.  While Zika was only identified in 2007 and Chikungunya in 2011,  dengue has been around for a long time but all three are seeing some alarming new trends. 

For dengue, usually outbreaks are seen in sporadic, explosions of 1 form of dengue (there are 4 main serotypes or strains that usually infect humans). However, in 2012 scientists saw epidemics involving all 4 serotypes of dengue. Multi-sera circulation of dengue virus is a particularly troublesome event because studies have shown that having antibodies to one strain of dengue significantly increases your chances of coming down with the most serious complications associated with dengue virus--Dengue shock syndrome and hemorrhagic fever. 2013 also saw the largest ever recorder outbreak of dengue. 

Zika virus produces slightly more mild response than west Nile or dengue, but is also a newer and less understood pathogen. However, in addition to much high case instances being seen in places like New Caledonia (as well as a reports of cases outside the observed scope of area that could not be counted) the virus is presenting in new ways. One concerning hallmark of the 2013-2014 outbreaks has been the high incidence of neurological complications--encephalitis and Guillain-Barre syndrome. 

Since Chikungunya virus's (CHIKV) identification in New Calendonia in 2011, it is now nearly endemic to the area. However, in 2012-13 the largest even epidemic was recorded in Papua New-Guinea. CHIKV does not frequently cause death, but it can cause severe fever, joint pain and sometimes debilitating  complications. While it does not seem as deadly as dengue, it has a much wider host range that includes rodents, monkeys and livestock. 

It is not known why the sudden increase in these diseases, but since these viruses are mosquito-borne, it seems possible that warmer climates causing larger mosquitoes populations could be a factor. 

--Lauren Sweet


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