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Hunting for mosquitoes in Puerto Rico
03:20 - Source: CNN

Story highlights

There are no treatments for mosquito-borne viruses such as Zika and dengue, so preventing mosquito bites is key

The greatest threats in the U.S. are West Nile, and dengue and chikungunya in Southern states

Avoid standing water and wear insect repellant to protect yourself

CNN  — 

When Zika virus made headlines because of its link with the neurological disorder microcephaly, it became the latest in a growing list of mosquito-borne viruses for Americans to worry about.

“Dengue, chikungunya and Zika are the ones that I’m very fearful of for the Gulf Coast states [such as Florida and Texas], and Zika is the most terrifying of all because of the horrific birth defects,” said Dr. Peter Jay Hotez, dean of the National School of Tropical Medicine at the Baylor College of Medicine.

There have been several dengue outbreaks in Texas, Florida and Hawaii over the past several decades. These infections can escalate to the point of causing severe pain, bleeding, shock and death.

Florida, Puerto Rico and the U.S. Virgin Islands have seen pockets of chikungunya in the last couple of years. It often afflicts the infected with debilitating joint pain.

Another mosquito-borne virus, West Nile, is everywhere in the United States, Hotez said. “It causes more severe disease like chronic kidney disease and neurological problems than people realize,” he added.

“Unfortunately, we do not have good antiviral drugs for any of these [viruses]. That makes prevention even more important,” Hotez said. Although a dengue vaccine was recently approved in Mexico, there are no vaccines against this so-called breakbone fever, or other mosquito-borne viruses, in the United States.

For Zika, prevention comes down to avoiding areas where the virus is spreading. To date, most cases of Zika in the continental United States have been in people infected while traveling. There are 10 cases of sexual transmission. The Centers for Disease Control and Prevention has advised pregnant women against travel to affected areas, because of the connection between viral infection and babies born with microcephaly, which causes small heads and developmental issues.

The Puerto Rico Department of Health has reported 925 cases of the virus in the U.S. territory. There have been 27 people hospitalized with the illness, six cases of Guillain-Barré Syndrome, one case of microcephaly and one death, all related to the virus.

However it is not possible to entirely avoid dengue and chikungunya in the United States.

The Southern United States, and especially the Southeast, faces the biggest threat. Aedes aegypti, the type of mosquito that can spread dengue, chikungunya and Zika, lives in this region, as well Central and South America, Africa, Australia and South Asia. Another type of mosquito, Aedes albopictus, can also transmit these viruses and is more widespread in the United States but is less of a threat because it does not feed on human blood as frequently and lives in less close contact with people. The Culex mosquitoes, the main vector for West Nile virus, are found all over the United States.

The good news is that all these viruses can be avoided by taking measures to prevent mosquito bites, which pass the viruses in their saliva. Whether it is the Aedes or the Culex, steps such as wearing insect repellant can stop them in their tracks.

What you can do at home

Americans can take a break from worrying about diseases from mosquitoes in the winter because Aedes and Culex mosquitoes are not active when it is cold, said Laura D. Kramer, professor in the School of Public Health at the State University of New York at Albany. But that break can be short-lived in places like the South. “As soon as it heats up [to 50 or 60 degrees Fahrenheit], mosquitoes will come back, and viruses can replicate in them,” Kramer said.

You are more likely to encounter Culex mosquitoes, which can carry West Nile virus, outdoors and at night. But you are at higher risk of bites from the Aedes mosquitoes, which can spread dengue, chikungunya and Zika, inside. That is because Aedes are active and feed during the day. “They come in the house for shade. … They live very close to people,” Kramer said.

Fortunately, most people in the United States close their windows when it’s hot and crank up the air conditioner. That probably goes a long way to reduce the risk of Aedes mosquito bites. The fact that people in Key West tend to keep their houses open probably worsened the dengue outbreaks in South Florida, Kramer said.

One of the most important things to do when the weather warms up is make sure you don’t have standing water outside your house, such as in a garbage can lid, a birdbath or trays of potted plants, Kramer said. Anything sitting around for more than five to seven days can be a breeding ground for mosquitoes, she said. (Properly chlorinated swimming pools deter mosquitoes.)

Kramer recommends dumping standing water at least once a week on dry ground: Any larvae in the water will die when the water evaporates and they dry out. You can also take a look at standing water to make sure it does not contain mosquito larvae, which are visible to the naked eye.

Many households hire exterminators or invest in misting systems that spray pesticides outside the house. This can be a temporary fix, at least for Culex mosquitoes, which buzz around outside the home, but not for Aedes, which are much more likely to be indoors, Kramer said. And even for Culex, if there are nearby houses where they can breed, “new mosquitoes will quickly repopulate [your] house,” Kramer added.

It may provide more lasting relief from Culex mosquitoes for an exterminator to spray outside all the houses in an area, Kramer said. However, it could be less useful when trucks, such as ones that municipalities hire, spray around neighborhoods if the pesticide does not reach the standing water and areas around homes where mosquitoes breed.

The U.S. Environmental Protection Agency and the CDC recommend taking a combination of approaches that includes eliminating standing water, and that could also include an outdoor misting system. However, there has not been enough research to know if the misting systems are effective at controlling mosquitoes and other insect pests, and they might end up killing butterflies, bees and other beneficial insects. In addition, the agencies warn that pesticides could pose human health risks if too much is used or they build up in the environment.

What you can do when you’re outside

There are a number of other important steps to stave off mosquitoes when you are outside. Cove