Chikungunya

Chicken-what? Unless you happen to be familiar with tropical diseases, odds are pretty good that you have no idea what I am talking about. Chikungunya is a viral disease that is transmitted by mosquitoes. The word “chikungunya” comes from the Kimakonde language of the Makonde people, which is an ethnic group that resides in parts of Tanzania and Mozambique, and means “that which bends up”. The name is meant to invoke an image of the suffering that the disease can inflict, describing the bent or contorted appearance due to athralgia, or joint pain, that is a common symptom of the disease. First described in 1952 following an outbreak in Tanzania, chikungunya has become a widespread and growing problem around the world, reaching epidemic proportions.

Chikungunya is an alphavirus, which means that it is a positive-sense RNA virus that belongs to the family Togaviridae. Briefly, what this means is that alphaviruses like chikungunya use a strand of RNA, rather than DNA, to store its genomic material. Alphaviruses are pretty fascintating in general, so I will try to make a separate post describing them in a little more detail. Anyhow, symptoms of chikungunya commonly include fever and joint pain that can last for a few days to a few weeks. It may be accompanied by a rash, nausea, fatigue and other aches. Although not usually fatal, it can cause fatal complications, especially in older individuals, and the debilitating effects can persist for months or even years. At the moment there exists neither a vaccine nor a cure for the disease. The primary prevention is to avoid mosquito bites if you are at risk, and for those infected, the only recourse is to attempt to treat the symptoms.

Looking at the map above, you might heave a grateful sigh of relief if you do not live in the highlighted area, or travel there routinely. Unfortunately, viruses and the mosquitoes that transmit them do not recognize such boundaries drawn on a map. Historically, chikungunya has relied upon the tropical mosquito Aedes aegypti (left) to serve as a vector, but a recent adaptation to make more efficient use of Aedes albopictus (below) as a vector is thought to be a contributing factor to the reemergence of the disease in a number of widespread epidemics that have occurred since 2004. Unlike Aedes aegypti, the mosquito Aedes albopictus is able to thrive in colder environments, and takes advantage of a wider range of breeding sites. The result is that Aedes albopictus has become established in Europe, as well as the Americas. This means that it is possible for viruses such as chikungunya to become established in these areas as well.

The ease with which viruses can be spread and develop into epidemics is clearly demonstrated by the introduction of West Nile virus into the United States. West Nile virus is another mosquito-borne, positive-sense RNA virus, though it belongs to the family Flaviviridae. First detected in New York in 1999, West Nile virus became established in the continental United States by 2003 and caused multiple outbreaks from 2003 to 2012, with the result being that it has become the most prevalent cause of insect-borne disease in the United States. It is not much of a stretch to predict that this could happen with other historically tropical diseases as well. Europe experienced its first major encounter with chikungunya when a Italy was hit by an outbreak of the disease in 2007. Now, local transmission of chikungunya has been reported for the first time in the Americas. The outbreak began in December of 2013 on the Caribbean island of Saint Martin, and since that time cases have been reported in a number of other islands. This outbreak is ongoing, so you might want to keep that in mind if you are considering a winter trip to a sun-soaked island beach in the Caribbean.

So to summarize, what we have here is mosquito-borne viral disease whose mosquito vectors are spread throughout the world. It is very likely that chikungunya and other similar diseases will continue to spread to previously unaffected regions, like the United States, just as West Nile virus has. There is no vaccine and no cure for this disease. Sounds like fun, right? This is one of the many reasons why funding for scientific research is so important. Pardon me while I stand on my soapbox for a minute, but vaccines for such diseases do not make themselves. There is little incentive for private companies to research, develop, test, and market a vaccine for a disease that mostly just affects poor people in developing nations on the other side of the world. Furthermore, if the drug does its job, people would only have to take it once. That is hardly a steady stream of income giving you a significant return on your investment, unlike medication for high blood pressure, cholesterol, depression, etc. There you have a drug that people take for the rest of their lives and can pay for, since the target audience predominately lives in more developed countries. The fact that such diseases do not directly affect us at this moment does not mean that we will never have to deal with it. Even if we care nothing for the suffering of the millions of people affected by this and other such diseases, and care only about our own self-interest, then we should should still care about this.

Thanks for reading!

Category(s): Science Stuff

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