Map Credit CDC
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Just over a month ago the World Health Organization issued a statement (see WHO: Chikungunya In Caribbean – French Part of St. Martins) describing 5 suspected and 2 lab confirmed cases of locally acquired Chikungunya in the Caribbean – the first time this mosquito borne disease had been reported in the Americas.
A few days later the CDC issued a HAN Advisory On Recognizing & Treating Chikungunya Infection, where the case count – as of December 12th – was listed as 12 confirmed cases.
Since then, the case counts have continued to rise – as have the number of islands affected. On Friday – Jan. 10th – the ECDC issued another update, indicating nearly 300 probable or confirmed cases.
Chikungunya – while rarely fatal - produces a fever, severe muscle and joint pain, and headaches. The symptoms usually go away after a few weeks, but some patients can sustain permanent disability, and some deaths have been reported.
First the report, then I’ll return with a bit more.
Epidemiological update: autochthonous cases of chikungunya fever in the Caribbean region
10 Jan 2014
An outbreak of chikungunya in the Caribbean region was reported from the French part of the island of Saint Martin on 5 December 2013. It is the first time that autochthonous transmission of the virus has been documented in the Americas. An ECDC risk assessment of the outbreak published on 12 December concluded that the risk of the disease spreading to other islands in the region was high. Since then, new chikungunya cases have been reported from several islands in the Caribbean.
As of 9 January 2014, the following number of cases has been reported:
- 201 probable or confirmed cases in Saint Martin (FR);
- 2 confirmed cases in Saint Martin (NL);
- 48 probable or confirmed cases in Martinique;
- 25 probable or confirmed cases in Saint Barthélemy;
- 10 probable or confirmed cases including one imported case from Saint Martin in Guadeloupe;
- 1 confirmed case imported from Martinique in French Guiana.
Chikungunya transmission was detected during an ongoing dengue outbreak in the Caribbean. Dengue and chikungunya viruses are transmitted by the same Aedes aegypti mosquito species. The naïve population, the presence of an effective vector in the region and the movement of people in and between islands are factors that make it likely the outbreak will continue to spread geographically and increase in numbers. Since the dengue outbreak is ongoing, clinicians and travel medicine clinics should remain vigilant regarding imported dengue and chikungunya cases from the Caribbean.
Until a decade ago, Chikungunya (aka `Chik’) was only found in parts of central Africa, and only occasionally sparked small outbreaks. In 2005, however, it jumped to Reunion Island in the Indian Ocean, where it sparked a major epidemic. Since then has spread rapidly to counties such as India, Thailand, Vietnam, Indonesia, Myanmar, Pakistan, and others in Asia and the Western Pacific.
Quite famously, Chik was carried by an international traveler from India to Northern Italy in 2007, where it sparked a local outbreak involving roughly 300 people (see It's A Smaller World After All).
While that outbreak was eventually contained, that introduction of the virus to Italy showed that Europe and the Americas were vulnerable to the importation of the virus, prompting the CDC & PAHO to publish a document in 2011 called Preparedness and Response for Chikungunya Virus Introduction in the Americas.
Mosquito-borne diseases are a particular concern because humans can often act as an amplifying host, and the United States is home to two particularly good mosquito species (Aedes aegypti, Ae. albopictus) for transmitting diseases. The relatively recent introduction and growing geographic range of the Aedes Albopictus mosquito (see below) in the United States has raised new concerns that once eradicated tropical diseases could become endemic once more.
Map showing the native habitat (blue) and recent spread (green) of the Aedes albopictus mosquito – Credit Wikipedia
The incubation period of Chik can be up to 12 days (avg 3-7), allowing infected, but asymptomatic travelers, plenty of opportunity to spread the virus. The good news is that in the middle of January, there are relatively few places in the United States where mosquitoes are active right now, limiting the chances of local transmission.
But as we’ve seen with West Nile Virus (and to a lesser extent, Dengue), when the right combination of multiple virus introductions, competent vectors, and favorable environmental conditions come together, formerly exotic diseases can get a foothold and even thrive here in the United States.
And, at least here in Florida, we aren’t that far away from the start of spring mosquito season.
