Are You at Risk for Mosquito-Borne Diseases?
If the faint humming sound of a nearby mosquito sets off an alarm in your head, there are some very good reasons it should. A mosquito bite can produce more than an angry, itchy red bump: The bugs are known to infect people with serious, and sometimes even fatal, diseases. Viral infections like Zika, chikungunya, and West Nile — as well as parasitic infections like malaria — are spread to people by certain types of mosquitoes. They also spread from people back to mosquitoes in areas where these diseases are rampant.
Some of the infections, such as malaria, are treatable, and there’s an effective vaccine against yellow fever. But other potentially dangerous mosquito-borne infections, like Zika, can’t be prevented with a vaccine, treated with medicine, or cured. So public health officials focus instead on controlling mosquito populations. Cutting down on mosquito breeding grounds by getting rid of standing water can help prevent disease outbreaks, as can pesticides that kill mosquitoes.
Here’s what you need to know about mosquito bites, the infectious diseases they cause, and prevention tips to help keep you safe
Zika is a viral disease named for the forest in Uganda where it was first identified. TheZika virus is primarily spread by bites from infected Aedes mosquitoes, but can also be transmitted through sexual intercourse, and from mother to fetus. Zika spread explosively throughout Latin America and the Caribbean in 2015 and is now a pandemic. While a Zika virus infection usually passes unnoticed, for about 20 percent of people it causes a brief, mild infection similar to the flu. Symptoms include a fever, rash, muscle aches, and red, itchy eyes. There’s no vaccine to prevent Zika, no specific treatment, and no cure.
The virus has affected pregnant women in Brazil, where Zika infection has been linked to the birth defect microcephaly — a condition that causes a baby to be born with an abnormally small head. The World Health Organization has called the clusters of birth defects related to Zika an international public health emergency. Because of the risk to growing fetuses, Centers for Disease Control and Prevention (CDC) travel alerts advise pregnant women not to visit the growing number of regions where Zika is spreading. In addition, the CDC says men who have a pregnant partner should use condoms if they live in or travel to areas with Zika infection. So far, most reported U.S. cases have been in travelers, according to the CDC.
Prevention tips: If you’re traveling to areas where Zika infection is ongoing, take measures to prevent mosquito bites. Use effective insect repellents, such as products with picaridin, lemon eucalyptus oil, or at least 20 percent DEET. Cover your arms and legs and stay in air-conditioned or screened areas in the daytime. The CDC advises pregnant women who’ve recently traveled to affected areas and feel ill to get screened for Zika.
Chikungunya is caused by a virus that’s spread by bites of infected Aedes aegypti andAedes albopictus mosquitoes (also called Asian tiger mosquitoes). In 2014, about 2,000 cases were reported in the United States — mostly in Florida — and more than a million were reported in the Caribbean and Latin America. Chikungunya symptoms include a sudden high fever and severe joint pain. The name chikungunya means “to walk bent over” because of the joint pain. It may also cause headache, rash, muscle pain, nausea, and fatigue. For about 15 percent of those infected who develop a chronic infection, chikungunya can seem like rheumatoid arthritis.
If you have the disease and are bitten by a mosquito while you’re ill, the mosquito can pick it up from you and continue the cycle of infection by biting someone else. But chikungunya doesn’t spread from person to person. As with Zika, there’s no specific treatment or vaccine to protect you from chikungunya infection.
Prevention tips: Cleaning up mosquito-breeding sites and preventing mosquito bites are your best bets for cutting risk of an infection. When you’re in areas that have chikungunya, the CDC recommends using insect repellent, wearing long sleeves and pants, and staying in air-conditioned or screened areas to avoid mosquito bites.
(Photo: The common house mosquito, Culex pipiens.)
West Nile Virus
The West Nile virus is passed on to people, birds, and horses from the bites of infected mosquitoes; it doesn’t spread from person to person. There were about 2,000 U.S. cases in humans in 2015, according to the CDC. Aedes, Anopheles, Culex, and other types of mosquitoes carry the West Nile virus, which is related to the Zika virus. One tip-off to public health workers in 1999 that West Nile had come to the United States was an increasing number of infected dead crows and jays, according to the CDC. Birds can get sick and die from the infection, but they don’t pass it on to people. In rare cases, people have become infected with the West Nile virus through blood transfusions, organ transplants, and lab exposure.
Only about 20 percent of people infected with West Nile have symptoms, which may include fever, headache, body aches and joint pain, vomiting, diarrhea, and rash,according to the CDC. But some — about 1 percent — develop long-term illness and meningitis (brain swelling) that can be fatal. There’s no specific treatment or vaccine for the West Nile virus.
Prevention tips: Protect yourself from mosquito bites that may carry the West Nile virus by wearing protective clothing and using insect repellent. Now that West Nile is widespread in the United States, be sure to mosquito-proof your home: Get rid of any standing water, and use screens on open windows and doors.
Dengue fever, which is transmitted through the bites of infected Aedes aegypti andAedes albopictus mosquitoes, sickens up to 400 million people worldwide each year,according to the CDC. Infection in the U.S. mainland is rare and usually travel-related; dengue is more common in Puerto Rico, Mexico, Latin America, Southeast Asia, and the Pacific Islands, including Hawaii. As of February 9, 2016, 250 confirmed cases of dengue fever had been reported on Hawaii’s Big Island in the state’s largest outbreak in over 70 years, prompting health officials to declare a state of emergency.
Dengue fever is caused by four related viruses and isn’t spread from person to person, except in rare cases of tainted organ transplants or blood transfusions. Symptoms are similar to those of other mosquito-borne diseases at first, including a sudden high fever, severe headache, eye pain, and bone, muscle, and joint pain. In severe cases, dengue hemorrhagic fever causes nosebleeds, bleeding gums, and bruises, as well as internal bleeding that can be fatal for about 10 percent of those infected. There’s no specific treatment for any of the dengue viruses, and no protective vaccine. Patients should avoid taking aspirin because of bleeding risk, but can take pain relievers like acetaminophen. In severe cases, they’ll need hospitalization to replace lost bodily fluids.
Prevention Tips: Avoid mosquito bites by eliminating standing water where they breed and using insect repellent, protective clothing, mosquito bed nets, and window screens,recommends the CDC. If you’re in an area where someone has dengue, protect them from mosquito bites to keep the insects from passing the virus on to you.
Malaria comes from a parasite (Plasmodium) that lives in both Anopheles mosquitoes and in people; it infects 200 million people and causes 500,000 deaths yearly worldwide. Up to 2,000 U.S. cases are reported each year — mostly in travelers, according to the CDC. Malaria was eradicated in the United States in the 1950s through a public health program that drained swamps and used insecticides.
If you’re infected with malaria, you may have a fever, headache, chills, and vomiting. Getting treatment right away is essential. Malaria is preventable by controlling mosquitoes, and curable by taking the right medication. Artemisinin-based combination drugs are approved to treat malaria, but exact treatment varies depending on where you were infected: In certain areas, some types of malaria are drug-resistant.
Prevention tips: If you’re visiting places where malaria is still common, you can take antimalarial drugs (mefloquine or chloroquine) to prevent infection. To find out which malaria drugs work best for your destination, look at the CDC’s country-specific tables. Be sure to use insect repellent and avoid mosquito bites.
Yellow fever is caused by a virus that’s passed on to people and monkeys by infectedAedes or Haemagogus mosquitoes. Although yellow fever is common in tropical areas of Africa and South America, it’s very rare in United States. And when it does occur, it’s usually travel-related, according to the CDC. If you pick up yellow fever, you may have symptoms including a sudden fever, chills, and a severe headache, along with back pain, body aches, nausea, vomiting, fatigue, and weakness. For about 15 percent of those infected, the infection doesn’t clear and causes jaundice — yellow skin and eyes for which it’s named — as well as bleeding, shock, and even fatal organ failure. There’s no specific treatment for yellow fever, and patients are told to avoid taking aspirin or other NSAIDs, like ibuprofen or naproxen, because they can make bleeding worse.Prevention tips: There is an effective vaccine for yellow fever, so protect yourself bygetting vaccinated before traveling to South America or Africa. Also use insect repellent and wear protective clothing to prevent mosquito bites.
Eastern Equine Encephalitis
The virus that causes Eastern equine encephalitis is passed along to people and horses through bites from Aedes, Coquillettidia, and Culex mosquitoes. The disease can be passed on to birds, too, but by another type of mosquito: Culiseta melanura. U.S. cases of Eastern equine encephalitis are rare — 3 to 21 per year, according to the CDC — and typically occur in people who have been near freshwater hardwood swamps along the Atlantic and Gulf coasts, as well as near the Great Lakes. Symptoms include fever, chills, joint pain, fatigue, and encephalitis (brain swelling), which can lead to vomiting, diarrhea, convulsions, and coma. The infection is fatal in about one-third of cases, according to the CDC, but it’s not spread from person to person. There’s no specific treatment for Eastern equine encephalitis, and no preventive vaccine.
Prevention tips: As with other mosquito-borne diseases, you can protect yourself from Eastern equine encephalitis by avoiding bites: Wear protective clothing, use insect repellent, install screens on windows and doors, and keep mosquitoes from laying eggs by cleaning up any standing water — even small amounts.
Dirofilariasis in People and Dogs
If you’ve taken your dog or cat to the vet, you’ve heard about heartworm (Dirofilaria) and the importance of prevention. But did you know that the infected mosquitoes that pass heartworms on to dogs, cats, and wild animals like raccoons could also infect you? The long, thin parasites called Dirofiliaria immitis infect people in rare cases, generally in the eastern and southeastern United States. The parasites don’t spread from person to person, but both animals and people can be infected through the bites of worm-infected mosquitoes, according to the CDC.
Heartworms damage the heart and lungs of dogs, the respiratory system of cats, and typically the lungs in people. Worms that die in lung arteries can cause dirofilariasis, a disease with symptoms including wheezing, coughing up blood, chest pain, and fever. Dirofilariasis is treatable and can be cured through surgery, which removes the lesions.
Prevention tips: Be sure to follow your veterinarian’s advice to prevent heartworm, and prevent mosquito bites by using insect repellent and insecticide-treated bed nets if there are mosquitoes in your area at night.