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Bug of the Week is written by "The Bug Guy," Michael J. Raupp, Professor of Entomology at the University of Maryland.

Chikungunya virus in the United States and its vectors: Yellow Fever Mosquitoes, Aedes aegypti, and Asian tiger mosquito, Aedes albopictus


Asian tigers like this one in my backyard bring hours of discomfort while working outdoors, even in the daytime.


Stories of the Chikungunya virus proliferated in the press this week as new human cases of an illness with a weird name appeared in New York and Texas. This virus belongs to a group of viruses called arboviruses owing to the fact that they are transmitted from one host to another by arthropods such as mosquitoes. Unlike some of humankind’s deadliest diseases carried by tiny two-winged vampires, such as malaria, yellow fever, and dengue, Chikungunya is not usually a fatal disease. According to the Centers for Disease Control, persons at the greatest risk are newborns, seniors, and folks with preexisting conditions including high blood pressure, diabetes, and heart disease.

Symptoms of the illness include fever, headache, muscle pain, rash, and joint pain. These symptoms are usually seen within a week of being bitten by an infected mosquito. While most of these symptoms resolve in days or weeks, joint pain may persist for months, or in some cases years. Joint pain associated with Chikungunya can be fierce and debilitating causing the unlucky victims to twist their body in pain, hence the name Chikungunya, which in an African dialect means contorted. At present there is no vaccine for the virus.

Why the recent uptick in Chikungunya in the US? 2013 was a breakout year for the virus in the Caribbean and more than a dozen island destinations have reported cases of Chikungunya. To date more than 400,000 suspected and confirmed cases have been reported in North, Central, and South America and the Caribbean.  Most of the cases in the United States involved travelers who returned from a foreign destination with the virus. However, the ingredients for Chikungunya to establish in the US are present, as evidenced by two recent cases in Florida involving people who had not recently traveled abroad.  Two important vectors for Chikungunya are common in Florida. The yellow fever mosquito, Aedes aegypti , made famous by Walter Reed, has been in the United States for centuries, while the Asian tiger is a newcomer having arrived in Texas in 1985 in a boatload of water-filled tires from Asia. The yellow fever mosquito is widely distributed in southern states and the Asian tiger is found from Florida to New England in the eastern United States and as far west as California. These two recent Floridian cases of Chikungunya likely indicate the presence of humans in the US harboring the virus, and then serving as meals for mosquitoes that in turn carry the virus to other humans. Fortunately, at present the number of humans infected by this route is infinitesimally small and certainly is no reason for panic.

What can you do to avoid contracting this unpleasant illness? My first suggestion is to consult a physician or reputable website about travel advisories regarding illnesses before you travel abroad. If your destinations include locations where Chikungunya is endemic, be sure to use personal protection when you are outdoors. Although mosquito bites are most common at dawn and dusk, Aedes aegypti and Aedes albopictus seek blood during daylight hours. Protect yourself from aggressive biters by wearing light-weight, long-sleeved shirts and pants when working or playing outdoors. Certain brands of clothing are pretreated with mosquito repellents such as permethrin. I have worn these in tropical rainforests where mosquitoes were ferocious and they really did help. Permethrin aerosols can be purchased and applied to clothing. Permethrin is not to be applied to skin.

Female mosquitoes use human blood to produce eggs. While feeding, viruses like Chikungunya are transmitted from the mosquito to the human in saliva injected into the wound by the mosquito.

Many insect repellents can be applied to exposed skin before you go outdoors. Some will provide many hours of protection, while others provide virtually none. The “gold standard” of mosquito repellents is the compound DEET. Higher percentages of DEET in a product generally result in greater levels and duration of protection. However, surveys indicate that some people avoid using DEET for a variety of reasons. In recent years many botanically-based products have come to the marketplace. Scientists discovered that wild tomato produces a compound, 2-undecanone, and created a product which prevents mosquitoes from landing on humans.  Picaridin is another active ingredient that provides long lasting protection against mosquitoes.  Other products containing oils extracted from lemon eucalyptus, Corymbia citriodora, and products combining oils of soybean, geranium, and caster bean protected people from mosquito bites as effectively as products containing DEET in field trials, but often for shorter time intervals. Products based on citronella and other essential oils derived from plants vary greatly in repellency with average protection times ranging from 5 minutes to 2 hours. So, you may have to apply these products more frequently to be protected.

Questions always arise regarding the use of repellents on children. Repellents carry precautionary statements on their labels. Always read the label carefully and follow directions and precautions exactly. You should help children apply repellents and consult a pediatrician before applying any product to the very young. Some products state not to let children handle the product and even some botanically-based products warn against use on kids under the age of 3. If your travel destinations include places where you will be wearing light clothing, be sure to use sunscreen to protect your beautiful skin from harmful UV and use insect repellent. Repellant is applied after, not before, the sunscreen and should be replenished after swimming. You can learn more about mosquitoes and avoiding their bites at these episodes of Bug of the Week:

July 22, 2013: It's biting time: Mosquitoes, Culicidae   

Aug. 20, 2012: Beware of Mosquitoes and West Nile Virus

July 20, 2009: Mosquito redux - Culicidae


Watch this video to learn tricks for reducing problems with mosquitoes around the home!


We thank Jenny Marder of PBS for providing the inspiration for this episode. Learn more about Chikungunya at the PBS website listed below. The excellent CDC website on Chikungungya was a resource for this episode as was the wonderful “Mosquito Information Website” of the University of Florida.