One of two highly competent vectors in the Americas
# 8606
While MERS and Avian Flu may eventually prove a more dangerous viral foe, for the Caribbean, Florida, and potentially other parts of North America a trio of exotic mosquito borne viruses pose a more immediate threat; West Nile, Dengue, and the new kid on the block . . . the Chikungunya Virus (CHKV).
West Nile arrived in New York City 15 years ago, and and very quickly began to spread across the nation. Today it has been reported in all 48 contiguous states.
From the USGS Factsheet on West Nile Virus
The headline last spring from the CDC was DVBID: 2012 Record Number Of West Nile Fatalities, where at least 243 deaths were recorded out of more than 5,000 infections. Given that most people experience only mild symptoms, and only the most serious are ever reported, the actual number of WNV infections was certainly in the tens of thousands.
Dengue, while a more recent arrival and claiming fewer victims in the United States, showed up in 2009 (see MMWR: Dengue Fever In Key West) after an absence of roughly 60 years, and over the past five years has been sporadically seen in Florida (see Florida: Dengue Forces Suspension Of Blood Donations In Two Counties), Texas, and last November we even saw a case of Locally Acquired Dengue In New York City.
In 2009 the Natural Resources Defense Council (NRDC) released a report outlining the risks that Dengue could re-establish itself in North America, that included this map showing the areas of the United States that are vulnerable to the introduction of Dengue.
Northern climes are far less likely to see dengue take hold than say, Florida or Southern Texas. Still, in the 18th and 19th century, both Malaria and Yellow Fever were endemic up and down the mid-Atlantic coast.
While Dengue and WNV will both be watched carefully during the upcoming mosquito season, the sudden arrival of Chikungunya into the Caribbean last fall (see CDC Update On Chikungunya In The Caribbean) has added a new threat to the mix.
Last month in Study: Chikungunya’s Growing Threat To The Americas, we looked at predictions that CHKV might be coming to a mosquito near you, an eventuality anticipated by the CDC/PAHO three years ago in their 161-page guide on preparing for the arrival of Chikungunya to the Americas (see Preparedness and Response for Chikungunya Virus Introduction in the Americas).
According to the ECDC, Chikungunya – which while rarely fatal, can cause prolonged fever and polyarthralgias (joint pain) - has now spread to more than a dozen Caribbean nations, and has caused more than 30,000 probable and confirmed infections (cite) over the past 6 months.
As you might expect, given its climate, its position as the gateway to the Caribbean, and that it receives millions of tourists every year - Florida is considered a likely first US battleground against any CHKV invasion. As part of their preparations for this unwelcome arrival, the Florida Department of Health recently held an Interagency Webinar on the CHKV threat.
Florida’s DOH Chikungunya Website contains some excellent resource materials from that webinar, including:
April 1st Interagency Webinar Presentations
Florida Surveillance and Response CHIK (1.1 MB PDF)
Mosquito Control Measures CHIK (2.0 MB PDF)
Epidemiology and Medical Importance CHIK (PDF)
For a recording of the April 1st training please contact Epi.Training@flhealth.gov and list "CHIK Training" in subject line.
Although we’ve seen sporadic cases of viremic CHKV infected travelers to the United States in the past (see 2011 CID Journal report Chikungunya Fever in the United States: A Fifteen Year Review of Cases), those numbers have been small (109 between 1995- 2009), and so far (unlike dengue and WNV), we haven’t seen any evidence of local transmission.
Imported CHKV in Florida – FL DOH
But with CHKV now in the Americas, the number of CHKV infected travelers to the United States will certainly increase, and any who are viremic (producing large quantities virus in their blood) while visiting regions where suitable mosquito vectors are present, could potentially introduce the virus to the local mosquito population.
Which is precisely what happened in Northern Italy in 2007, when a single infected traveler returning from India provided a blood meal to a local mosquito that set off a chain of infection that eventually affected 300 people (see It's A Smaller World After All).
One of the best reviews of CHKV that I’ve seen can be found in the slide presentation - Epidemiology and Medical Importance CHIK (PDF) – a few excerpts which you will find below:
Chikungunya, like Dengue, WNV and other mosquito borne illnesses are largely preventable.
While the overall risk of contracting a mosquito-borne illness anywhere in the United States remains very small, with no vaccines available, and scattered cases of Dengue, West Nile Virus, EEE, SLEV, and now the specter of Chikungunya arriving in the near future - Florida’s Health departments urge people to always follow the `5 D’s’:
Good advice in Florida this during this spring and summer, and anyplace else mosquitoes can be found.
