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Beyond the Itch: These 8 Mosquito-borne Illnesses Pose a Major Health Risk

Jun 13, 2023

Is there anything more irritating than mosquitoes buzzing around while you’re trying to enjoy your time outside? Well, maybe their itchy bites! Mosquito bites can last anywhere from a few days to a week or more. The irritation is caused by our immune system’s response to the mosquito’s saliva and can be exacerbated by an allergic reaction.


Unfortunately, the effects of a mosquito bite can be significantly more severe than an itchy raised bump. Because mosquitoes feed on many hosts–humans and animals–throughout their lifetime, they are carriers of several harmful diseases. These 8 mosquito-borne illnesses can pose extremely serious health risks to humans and pets.

1. West Nile Virus

West Nile virus is the most common mosquito-borne illness in Canada and the United States. It is spread by mosquitoes from birds to horses and humans. Fortunately, most people who contract West Nile virus will never experience any symptoms. About 1 in 5 people who contract West Nile virus will develop a fever and/or other mild symptoms like headache, body aches, joint pains, vomiting, diarrhea, or rash. A significantly smaller portion of infected people will develop a severe illness affecting the central nervous system such as encephalitis or meningitis.

2. Chikungunya Virus

The chikungunya virus causes fever, joint pain, headaches, muscle pain, and rashes. It is primarily spread by mosquitoes and has been present in North America since around 2013, though it is fairly rare. Mild symptoms may go unrecognized, but serious symptoms, including debilitating joint pain, can last for weeks, months, or years. Chikungunya can also cause eye, heart, and neurological complications.

3. Dengue Virus

Dengue is common in tropical climates, including tropical areas of North America. Mild symptoms of dengue include fever, aches and pains, and rashes, usually lasting about a week. Severe dengue can be fatal or result in shock and internal bleeding. About a quarter of people who are infected with dengue will develop symptoms, and those who have already had a mild case are more likely to have a severe case if they are infected again.

4. Eastern Equine Encephalitis Virus

Eastern equine encephalitis is rare in North America, but not unheard of. It’s extremely serious. About a third of Eastern equine encephalitis cases are fatal, and many survivors will have long lasting neurological impairments. Mosquitoes transmit this illness from birds in freshwater hardwood swamps to humans and horses (hence the word “equine” in the name).

5. La Crosse Encephalitis

Most cases of La Crosse encephalitis will be asymptomatic, but those with symptoms can include a few days of fever, headache, nausea, vomiting, fatigue (tiredness), and lethargy. More severe cases can result in infection of the brain, and less than 1% of cases are fatal. La Crosse encephalitis has been observed in upper Midwestern, Northeastern, mid-Atlantic, and Southeastern states of the United States. Mosquitoes transmit this illness to humans from small mammals, such as chipmunks and squirrels.

6. St. Louis Encephalitis

St. Louis encephalitis can occur anywhere between Canada and Argentina, though it is most common in the United States. Most cases are asymptomatic, but some cases will cause fever, headache, nausea, vomiting, and tiredness. Some people may develop neuroinvasive disease, such as encephalitis or meningitis. Rare cases can result in long-term disability or death. St. Louis encephalitis is transmitted to humans by mosquitoes who have fed on infected birds, including those commonly found in suburban areas, like sparrows, pigeons, blue jays, and robins.

7. Malaria

About 2,000 people in the United States and about 490 people in Canada are diagnosed with malaria each year. Malaria is caused by a parasite that infects mosquitoes who in turn bite and infect humans. Malaria may result in a wide variety of symptoms, ranging from absent or very mild symptoms to severe disease and even death. It is generally considered to be curable if it is diagnosed and treated promptly and correctly. 

8. Zika Virus

Symptoms of Zika virus, including fever, rash, joint pain, and red eyes, are generally mild. However, in pregnant women, Zika virus can be transmitted to the fetus and can result in birth defects. Fortunately, following an outbreak of Zika virus in the United States in 2016-2017, there has been no known transmission of Zika virus in North America since 2019.

Preventing Mosquito-borne Illness

While most of these mosquito-borne illnesses are fairly rare, they can result in major health risks, so it’s important to take reasonable precautions to prevent them by reducing your exposure to mosquitoes and their potentially dangerous bites. With Mosquito Hero’s effective mosquito control programs, you get custom, targeted control and monthly service from a trained professional, effectively reducing the mosquito population in your yard. 


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