Credit FL DOH
# 7031
Although much of the rest of the country has endured a long procession of bitter winter storms, Florida has enjoyed one of its milder winters in recent years. While great for tourists and residents alike, balmy winters make a great environment for mosquitoes as well.
Overnight, local media has been reporting on the EEE (Eastern Equine Encephalitis) infection of an 11 year-old boy from Hillsborough County (Tampa) which began (unusually, even for Florida) in February.
The boy – who is now recovered - spent three days in intensive care after apparently being bitten by an infected mosquito during a field trip to a local nature preserve (see local ABC News coverage).
This marks the first EEE case in Hillsborough County since 2010 (see Third Florida EEE Death in July). In January of this year, another EEE case was reported in a Levy County resident (see Florida Arbovirus Surveillance Report).
EEE (Triple `E’) is an often serious, but exceedingly rare illness in humans. It is one of more than 100 kinds of arbovirus (viruses transmitted by arthropods e.g., Mosquitoes, sandflies, midges, or ticks).
According to the MMWR (here), between 1999 and 2008 there were a median of seven (range: 3--21) EEE cases (not deaths) reported in the United States each year.
In addition to EEE, West Nile virus (WNV), La Crosse virus (LACV), and St. Louis encephalitis virus (SLEV) also circulate at low levels in the United States.
While the number of yearly cases is low, the distribution of EEE in the United States far ranging. Often, the heaviest EEE activity is reported in northern states.
You may recall that last October, I blogged on the surprising role that snakes play in the ecology of the EEE virus (see A Disease Detective Story: Figuring Out Where EEE Spends The Winter).
To keep things in perspective, on average 58 people are struck and killed by lightning each year in the United States, and Bee stings account for an additional 40 deaths each year.
Which isn’t to minimize EEE or any of the other arboviruses, or to suggest that people not take precautions against mosquitoes, but is simply a reminder that a lot of the diseases we talk about in this column are pretty rare.
Hillsborough County Health Department has issued a mosquito advisory based on this most recent case.
For Immediate Release
March 25, 2013
Compared to Dengue and West Nile Virus, the ecology and epidemiology of EEE is fairly complicated.
The natural host for the EEE virus are songbirds, which can become infected generally without suffering ill effect. The virus is spread among these birds by the blood feeding of female mosquitoes (males don’t bite).
After an infected mosquito feeds on a bird, the bird becomes infected and the virus begins reproducing. After a few days, and for only a few days, the bird’s bloodstream contains enough virus to infect subsequent mosquitoes that feed on it.
Culiseta melanura, which means "curly black hairs", is the species of swamp mosquito that serves as the primary vector for this virus among birds.
It, however, isn’t usually predisposed to d to biting humans.
So it generally requires a secondary type of mosquito - one that isn’t quite as picky a feeder - such as the Aedes albopictus or Coquillettidia perturbans `salt and pepper’ mosquito, to bite an infected bird in order to move it into the equine or human population.
Humans and horses don’t develop a high enough viral EEE titer in their bloodstream to pass on the virus if they are subsequently bitten by a mosquito, so they are considered a `dead-end host’.
For more on this fascinating topic, there’s an absolutely terrific multimedia presentation on arboviruses in Florida.
It is a narrated slide show, by Rebecca Shultz, the Arthropod-borne Disease Surveillance Coordinator for the Florida Department of Health, and it covers EEE, SLEV, and West Nile Virus.
The presentation runs just over 20 minutes. The transcript is here. Click the image below (or this link )to go to the slide show, and turn on your speakers.
Highly recommended.
2012 was a near-record year for West Nile Virus across the nation as well, which resulted in at least 5,387 confirmed cases, including 243 deaths(see DVBID: Final West Nile Report For 2012).
Which is why the State Health Departments around the nation continue to urge residents and visitors to follow the `5 D’s’:
