Monday, June 15, 2015

An Early Look At West Nile Activity


Credit CDC 


# 10,212

While Ebola, MERS, and avian flu often make the big headlines, the average person faces a far greater health threat from a mosquito bite than from one of these novel viruses.  Every year in the United States thousands of people are infected by mosquito borne diseases, and while we see a handful of EEE, Dengue, or STLEV cases  the biggest numbers are wracked up each year by the West Nile Virus.


Introduced to this country in 1999 – ostensibly by a viremic traveler in New York City – the virus has since spread across the entire lower 48 states, and makes a yearly appearance in early-to-mid summer.


Some years are admittedly much worse than others, with 2012 seeing more than 5600 cases of West Nile virus disease reported to the CDC, including 286 deaths.  Last year, only 85 deaths were reported, while in 2013 there were 111 fatalities (cite).


Remarkably,  there have been roughly the same number WNV fatalities in the United States since the spring of 2012 as have died from MERS globally over the same time period.


About 80% of those infected with WNV experience at worst only mild, or sub-clinical symptoms. Most of the rest may experience a brief febrile illness (West Nile Fever).  Both are likely highly underreported.


A very small percentage (perhaps 1%) of those infected develop WNV neuroinvasive disease (WNND), a form of encephalitis that can sometimes prove fatal. Those over the age of 50 appear to be the most vulnerable to the most serious form of the illness, and as most of those are hospitalized, those numbers are the most reliable.

About 3 weeks ago  we saw the Texas DSHS Announces First Neuroinvasive West Nile Case Of 2015.  Today we have the first summary of 2015 cases from the CDC. Typically, these numbers don’t really take off until late July or August.




As we do every summer, we’ll be following the spread of mosquito-borne pathogens such as Dengue, Chikungunya, Malaria, WNV, SLEV, and EEE  along with tickborne diseases like Lyme, SFTS, and the Heartland Virus. 


Although the overall risk of contracting a mosquito-borne illness the United States remains pretty small, scattered cases of West Nile, EEE, SLEV, La Crosse Encephalitis, and a few others are reason enough for health departments across the nation to urge people to follow the `5 D’s’ of mosquito protection:



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