Emerging viral disease in the Carribean
This news alert has been popping up via several news sources over the past few days. I first saw it via the New York Times, however the video clip is a BBC news report detailing the regional response to this outbreak. Several islands in the eastern Caribbean Sea have been experience significant outbreaks of Chikingunya fever, a mosquito transmitted disease that fortunately has a relatively low mortality rate but a pretty high rate of infection. Indeed, the ease of infection in humans and the high level of debilitating symptoms of disease led several governments to consider Chikingunya virus in biowarfare programs before these were banned by international treaty. What makes this outbreak alarming is the rapid spread that the disease is making from island to island, and the fact that this is the first time that the virus has been seen outside of its endemic region in sub-Saharan Africa.
Chikungunya fever is caused by an RNA genome virus; the most closely related virus that might be familiar to BIO230 students is the Rubella, or German Measles virus, which is itself showing a resurgence in the US due to failure to vaccinate. Unlike rubella, Chikungunya virus is transmitted by the mosquito when it bites someone after having a blood meal on an infected individual. The incubation period is usually under a week, then the patient will exhibit a high grade fever, fatigue, and moderate to severe joint pain. The acute phase fever will generally resolve itself within a week or so, however in Chikungunya the joint pain will persist for weeks to months afterward. The initial symptoms of fever and pain lead many clinicians to initially diagnose Chikungunya fever as Dengue fever as the two diseases share a broad geographic region, however the prolonged joint pain is NOT characteristic of Dengue. This fact has led some epidemiologists to suspect that the incidence of Chikungunya fever is more significant that what has been reported.
There is currently no treatment for Chikungunya fever other than supportive therapies including rest, fluids, and non-aspirin pain relief. There is also not currently a vaccine for Chikungunya fever, although some clinical trials do show promise. Infection and recovery from Chikungunya fever confers life-long immunity to reinfection, so the current outbreak in the Caribbean does offer the opportunity to observe the spread and control of a highly infectious agent in an immunologically naive population. The initial outbreak was on the island of St. Martin in December 2013, with 3700 confirmed or suspected cases on St. Martin and several other eastern Caribbean islands. The Centers for Disease Control and Prevention have prepared a response document to the current outbreak. The spread of the disease into North America is unlikely, but not impossible. The virus is transmitted by two mosquito species, Aedes aegyptii and Aedes albopictus, both of which are found in the southern United States however mosquito control measures are effective at limiting the numbers of these insects. In order for an outbreak to occur, it is also necessary to have a reservoir of infected hosts for the mosquitoes to bite–the outbreak is dependent on having a population of infected individuals AND adult mosquitoes to maintain the outbreak. Consequently, in geographic areas where mosquito activity is seasonal, these outbreaks will stop as the mosquitoes are killed by cold weather. The main danger to US residents is with travel to Chikungunya outbreak regions, and the CDC recommends that all such travelers practice good insect avoidance measures.