They can ruin your day at the beach, that perfect hike on a gorgeous summer afternoon or a long-planned camping trip, but mosquitoes also have a much larger impact — they’re actually the deadliest animal in the world, far more lethal than humans, snakes or sharks, as Bill Gates pointed out on his blog earlier this year. And the little insects have a big economic impact.
Mosquito-borne diseases kill about 725,000 people around the world every year, with most of those deaths — more than 600,000 — due to malaria. That disease causes billions of dollars in lost productivity every year, Gates noted, providing the chart below.
Malaria is no longer a threat in the United States, but this country is currently seeing a seasonal resurgence of West Nile virus, another mosquito-borne illness. While most people infected by the virus do not develop any symptoms, roughly 20 percent will come down with fever and aches or, in more severe cases, even serious neurologic illnesses such as encephalitis and meningitis.
Mosquitoes also carry other viruses that can cause other forms of encephalitis as well as illnesses such as dengue, Rift Valley fever and yellow fever that are rarer in the U.S. The first case of Chikungunya (pronounced chicken-gun-yay) virus in the U.S. was reported last year and New York State just reported its first case.
Related: Chikungunya, and Other Diseases You Now Have to Worry About
West Nile virus is the most dangerous in the U.S., though. First detected in 1999 in the New York area, the virus has since spread to virtually every region of the country. From 1999 through 2013, more than 17,000 cases of the neuroinvasive form of West Nile have been reported, and those cases resulted in more than 1,500 deaths, according to the CDC. Another 22,000 cases of non-neuroinvasive disease have caused more than 100 other deaths. A vaccine against West Nile does not exist, though scientists are working on developing one.
A 2002 outbreak of West Nile virus caused 4,156 cases nationwide, including 329 in Louisiana alone. The Center for Disease Control and Prevention (CDC) totaled the costs attributable to the epidemic in the state, including medical and nonmedical costs, to $20.14 million. A 2005 outbreak of West Nile in California had an economic impact that totaled $2.98 million, according to the CDC. That price tag includes medical costs, lost productivity, anti-mosquito spraying and other costs.
The first reported human case of West Nile virus this year was in Texas and since, human cases have been reported in New Mexico and Ohio. In 2014, 2,085 cases of the virus were reported in 42 states and the District of Columbia, with 84 deaths.
Texas and California may be particularly prone to virus cases this year, according to The Wall Street Journal. The recent catastrophic floods in Texas are attracting mosquitoes earlier and in greater numbers than usual. Not all mosquitos carry the West Nile Virus, but a higher mosquito population increases the likelihood of infected mosquitos.
Counterintuitively, the prolonged drought in California is also creating a hospitable environment for the mosquitoes, causing the insect population to rise rapidly. The bugs are attracted to the stagnant water that sits in storm drains, empty pools and almost anywhere somebody is trying to conserve water. “The lack of water could have caused some sources of water to stagnate, making the water sources more attractive for mosquitoes to lay eggs,” Dr. Karen Smith, director of the California Department of Public Health, said earlier this year. In addition to the drought, hotter summers and milder winters are exacerbating the issue.
California had 801 human cases of West Nile virus last year, the second highest total since the virus first reached California in 2003, according to the California Department of Public Health, and 31 people died from the disease, more than in any previous year.
Related: GSK Seeks Approval for World’s First Malaria Vaccine
To prevent exposure to mosquito bites and West Nile virus, health officials recommend that people practice the “Four Ds”:
1. DEET: insect repellants containing DEET, picaridin, IR3535, and some oil of lemon eucalyptus and para-menthane-diol products provide longer-lasting protection, according to the CDC.
2. DRESS: Wear long sleeves, long pants and socks when outdoors, weather permitting. Spray repellant containing permethrin or another EPA-registered repellent on the clothing for extra protection.
3. DRAIN: Empty standing water from flower pots, gutters, buckets, pool covers, pet water dishes, old car tires and birdbaths on a regular basis, the CDC advises.
4. DUSK AND DAWN: These are peak mosquito biting times, so limit your time outdoors during these hours.
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