Mosquitoes have earned a reputation as one of life’s most annoying insects. They seem to be ever-present when we’re trying to enjoy a warm evening outdoors, biting us and causing us to itch, and can create a persistent, loud buzz that seems to defy their body size when they’re trapped in a room with us. In addition to being an annoyance, however, mosquitoes are increasingly becoming a health risk with the emergence of the Zika virus.

Mosquitoes belong to the order of Diptera, or True Flies. Both male and female mosquitoes feed on plant nectar, but the females have a long, piercing proboscis that they use like a needle to extract blood when they bite. The blood they extract is a protein source for their eggs. Mosquitoes use temperature, body odor, movement, and exhaled carbon dioxide to locate potential victims. They become carriers of infectious disease when they bite an infected person or animal; the blood they extract enters their circulatory system through their mid-gut, and from there enters into their salivary glands. The redness and itching we experience from mosquito bites is actually an allergic reaction to their saliva.

There are over 3,000 species of mosquito in the world, but only three are responsible for the spread of human diseases. The Aedes genus is the carrier of the Zika virus, which includes the Asian tiger mosquito and the yellow fever mosquito. These mosquitoes are known as aggressive daytime biters, are also vectors for  yellow fever, dengue, and encephalitis, and are commonly found in the Gulf Coast region of the United States, but have been found as far north as Connecticut and Maine. The Asian tiger mosquito has been found in Hawaii as well as the mainland U.S.

While most mosquito caused human disease is limited to undeveloped countries, there have been cases that become widespread, causing alarm around the globe. This was the case with the West Nile virus previously, but in recent months the threat of Zika has become of chief concern to many. The World Health Organization even declared it an international health emergency after the spread of the virus in the last two years.

The Zika virus was first discovered in 1947, and gets its name from the Zika Forest in Uganda. Symptoms of the virus include fever, headaches, rash, red eyes (conjunctivitis), and joint or muscle pain. The symptoms may last up to a week, but typically don’t require hospitalization.

Zika is believed to have spread from Africa to mainland Asia, then to the Pacific islands, and from there to South America and now into North America. The first indications that the virus have more dire effects were discovered in French Polynesia in 2013, where 11% of the population had symptoms severe enough to require medical care. This was when Zika began to be suspected of causing neurological symptoms after 40 infected persons contracted Guillain-Barré syndrome.

The concern over Zika grew even more last year, after being linked to an explosion of microcephaly cases in South America. Microcephaly is a neurological condition in which an infant’s head is significantly smaller than normal and they suffer from incomplete brain development. Zika is believed to be passed from a pregnant mother to the fetus when the virus attacks fetal nerve cells through the walls of the placenta. Pregnant women should be especially careful about mosquito bite prevention, but the virus can also be spread sexually. Men who have been infected by mosquito bites can infect their partner, as viral RNA has been found in semen more than two months after initial symptoms. Women who recover from Zika virus before becoming pregnant are believed to be immune, however, which would negate any harm to the baby.

It is believed that over half of the human population on Earth live in areas where the mosquitoes capable of spreading the virus are found. During the first week of infection, the virus is in the blood of infected persons and can be passed to mosquitoes and then on to other people. There is no vaccine for Zika virus, and no known cure for either microcephaly or Guillain-Barré syndrome.

Until populations have built up a herd immunity against the virus, the best approach to dealing with it is in prevention. Pregnant women, women who may become pregnant, and their sexual partners should be especially cautious. Preventative measures include wearing clothing that covers the arms and legs, using mosquito repellent on both your exposed skin and on your clothes, using mosquito netting around bedding when necessary, or avoiding areas of greater insect activity. For men who have been infected, wearing condoms during sexual activity can prevent the virus from spreading to partners.

Since mosquitoes breed around water, laying eggs even in as small an amount as a bottle-cap full, the key to prevention is removing any standing water around your home. Be sure to check vases, potted plants, buckets, pools, and bird baths, and empty or filter this water routinely. Pesticides may also be used to kill adult mosquitoes and their larvae.

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