In Case You Need Another Reason To Hate Mosquitos …

Last week, Maggie Koerth-Baker warned that chikungunya, a mosquito-borne disease that’s not typically fatal but currently has no cure, is inevitably making its way to the US:

The virus has been known since the 1950s, but because it was largely non-lethal and largely confined to developing countries in Africa and Asia, the Western medical establishment didn’t much care about it until 10 years ago. That’s when chikungunya showed up on the French-controlled island of La Réunion, in the Indian Ocean, where it infected 40 percent of the population. Since then, it’s exploded in parts of Asia where it hadn’t been seen in decades (and other parts where it hadn’t been seen at all), reached Australia and Taiwan, and made landfall in Italy and France. And all of that was before the outbreak in the Caribbean.

So what changed? The sudden spread of chikungunya seems to be related to two things. First, the virus itself mutated. The strain that’s spreading around the world is different from the one that hung around sub-Saharan Africa. Specifically, it’s much more efficient at replicating itself in the guts of mosquitoes. That seems to have increased both its ability to move into new places and its ability to be carried by different species of mosquito.

That same day, the CDC announced the first locally acquired case of the virus in Florida. Vanessa Vitiello Urquhart explains why medical entomologists (like her wife Cassandra) are freaking out:

To understand why it’s chikungunya, not dengue, that makes entomologists so nervous, you’ll need to know a bit about another mosquito; Aedes albopictus (more pronouncably known as the Asian tiger mosquito). The Asian tiger mosquito is an invasive species that has spread over much of the eastern half of the United States since its introduction in 1985. These back-and-white-striped jerks are capable of spreading all sorts of diseases, including West Nile, dengue, and yellow fever. However, they often do so pretty inefficiently, with viruses found in only the tiniest minority of the mosquitoes tested. In the case of chikungunya, however, at least one strain has been shown to spread as easily in tiger mosquitoes as in Aedes aegypti. …

Adding to the reasons for alarm is the fact that chikungunya doesn’t need a reservoir—it can be spread directly from one human host to another. This is in contrast with several other mosquito-borne pathogens, including West Nile virus, which needs to replicate inside a bird before it can pass from a mosquito to a human. The special characteristics of tiger mosquitoes once again exacerbate the problem—these particular mosquitoes prefer feeding off of, and living close to, humans. (Many mosquitoes, in contrast, feed opportunistically on humans, while primarily targeting other animals.) Tiger mosquitoes are also daytime feeders, which means that while other species are taking a break, preferring to feed at dawn or twilight, the tigers keep chomping during the times of day when humans are most active.