Chikungunya’s Spread in the Americas – Credit PAHO
Up until 2005, Chikungunya was an obscure mosquito-borne disease that only sporadically caused outbreaks in Eastern and central Africa. Then, in an unexpected plot twist , a mutation in the envelope protein gene (E1-A226V) of the virus allowed Aedes Albopictus or `Asian tiger’ mosquito to transmit the virus more efficiently (see A Single Mutation in Chikungunya Virus Affects Vector Specificity and Epidemic Potential).
After decades of of having limited impact, CHKV began to tear across the Indian Ocean with a vengeance, first sparking an epidemic on Reunion Island where it reportedly infected about 1/3rd of that island’s population (266,000 case out of pop.770,000) in a matter of a few months, before moving on to Southeast Asia.
In 2007, a viremic traveler returning from India introduced the virus to Northern Italy (see It's A Smaller World After All), sparking a short-lived outbreak in the province of Ravenna, where nearly 300 cases were reported. Since then we’ve seen further spread of the virus across Southeast Asia and the Pacific, and most recently, CHKV’s jump to the Americas.
Chikungunya arrived in the Caribbean on the French part of St. Martins late last fall – but quickly spread to other islands in the Leeward and Windward chains - and has now appeared in Central and South America. In July, the first locally acquired case was reported in Florida (see CDC Statement On 1st Locally Acquired Chikungunya In United States).
While rarely fatal, the CDC describes the symptoms of infection as lasting a few days to a few weeks, producing `debilitating illness, most often characterized by fever, headache, fatigue, nausea, vomiting, muscle pain, rash, and joint pain’, although some may experience `incapacitating joint pain, or arthritis which may last for weeks or months.’
PAHO’s latest numbers indicate more than 580,000 cases have been reported across the Americas since December, resulting in 37 deaths, although this is likely an undercount. While the virus hasn’t gained a firm foothold in North America yet, as we’ve seen in Florida Prepares For Chikungunya, many health officials fear it is only a matter of time.
All of which serves as prelude to a report that was published yesterday in the journal Clinical Microbiology & Infection (CMI) called:
R. N. Charrel1, I. Leparc-Goffart2, P. Gallian1,3 and X. de Lamballerie1
Considering the worldwide dissemination of Aedes mosquitoes, several years ago some of us anticipated the globalization of Chikungunya virus through invasion of the Americas, and stated that the question was not whether it can happen, but when it will happen .
Although not terribly long, this open access report provides four points for public health officials to consider with regards to this emerging virus.
- There is a high risk for the introduction of CHKV to new regions, for endemization, and for subsequent local transmission of the virus.
- Retrospective laboratory analysis have uncovered a small, but significant number of serious clinical presentations of the virus, including respiratory failure, kidney failure, meningoencephalitis, and other CNS symptoms.
- There are open questions regarding the safety of the blood supply in endemic areas, particularly given the potential for asymptomatic infection.
- While processing a far greater capacity to spread, CHKV is often ignored by the media and the public due to coverage of more high profile disease threats like Ebola and MERS.
The report can be read in its entirety at this link.