Michelle Healy

USA TODAY

The announcement Wednesday by Harris County, Texas health officials that a mosquito had tested positive for the chikungunya virus is the latest evidence confirming its presence within the U.S.

The positive test is believed to be the first nationally, says Kristy Murray, associate vice-chair of research at Texas Children's Hospital in Houston — which is in Harris County — and director of its Laboratory of Vector-borne and Zoonotic Diseases.

"Where before we were very concerned about people traveling from areas, especially the Caribbean where there's a tremendous (chikungunya) outbreak going on, now this means that someone could be sitting in their own backyard in Houston and become infected — no travel required," says Murray.

"Year to date, we have (tested) over 450,000 mosquitoes (for various viruses). We're talking about a lot of mosquitoes, says Umair Shah, executive director, Harris County Public Health & Environmental Services. "This is the first time we found it."

It has not been been determined whether the mosquito that tested positive obtained the virus from an infected person in the state or if it traveled to the country via a shipping or cargo container of some sort, says Shah. "It's too early to tell and it's hard to tell."

Houston can be considered a "high-risk area" for the chikungunya (pronounced chik-un-GUHN-ya) virus for several reasons, says Murray: both species of the Aedes mosquito (aegypti and albopictusandi) capable of transmitting the virus are found there; it is very densely populated; and it has a very hot, humid summer climate. "Honestly, it can be difficult to avoid mosquito bites here," she says.

As of Aug. 5, the Centers for Disease Control and Prevention reported a total of 484 chikungunya cases nationwide. Four locally transmitted cases, including the nation's first, have been reported from Florida. All other cases occurred in travelers returning from affected areas in the Caribbean or South America, the Pacific Islands, or Asia.

As of Aug. 6, the Texas Department of State Health Services confirmed 10 human cases of the virus. All of cases were imported.

According to the CDC, chikungunya is not contagious from person to person, is typically not life-threatening and will likely resolve on its own.

Symptoms include fever and joint pain within a week after a person is bitten by an infected mosquito. Patients can also develop severe headaches, muscle pain and swollen joints. There is no vaccine and no specific treatment.

The mosquito that tested positive in Harris County means "we need to start actively looking for cases in the area, make sure doctors are aware of what to look for and how to test for cases (and) that people are aware of the symptoms, so if they do get sick they can go seek medical care and become tested," says Murray.

And the public needs to do its job by taking preventive measures, including using mosquito repellents, covering exposed arms and legs, and ridding nearby areas of all standing water, says Shah.