Common Mosquito Diseases

Author: Mosquito Squad

Mosquitoes kill more humans than any other animal, around 700,000 to one million a year. In the United States, while we are extremely lucky to consider mosquitoes more of a nuisance than a deadly threat, we have to remain informed and vigilant. Perhaps the most well-known mosquito-borne virus, malaria, was eradicated in most of the United States in the 1950s. With the Zika outbreak in 2015 and the impacts of climate change upon us, we should all be prepared, educated, and aware of the most common mosquito viruses and mosquito-borne illnesses.

How Does a Mosquito Pass on a Virus?

When a mosquito bites you, it injects a small amount of anticoagulant and saliva into your blood. Just as our immune systems attack viruses, mosquitoes have immune systems, too. First, the mosquito’s own systems fight the virus. If it’s immune system doesn’t win, that’s when it might pass on the virus to you. The virus first must survive the mosquito’s gut, then particles have to escape through the salivary gland. For example, in areas where mosquitoes carry West Nile virus, about 1 out of 500 mosquitoes are infected. Furthermore, if bitten by an infected mosquito, the chance of a person developing the illness is roughly one in 300.[1]

The Centers for Disease Control says the most effective way to avoid getting sick from viruses spread by mosquitoes is to prevent mosquito bites. What better way to do that then to make sure you have fewer mosquitoes in your community?


Malaria is by far the most common mosquito-borne illness affecting humans. Technically, it is caused by Plasmodium parasites. According to the World Health Organization, nearly half of the world's population is at risk of malaria. In 2015, there were roughly 212 million malaria cases and an estimated 429,000 malaria deaths. Many regions of Southeast Asia and Africa are extremely vulnerable to this mosquito population due to climate and geography. Mosquito Squad supports Malaria No More and has raised more than $450,000 to help fight malaria in Africa.

In 1947, the U.S. Public Health Service started its concentrated assault on malaria in the southeastern United States. The National Malaria Eradication Program consisted primarily of DDT application to the interior surfaces of rural homes. In two years, the program treated more than 4 million homes. By 1949, the country was declared free of malaria as a significant public health problem.

DID YOU KNOW? The Center for Disease Control was actually formed from the Office of Malaria Control in War Areas. In 1942, malaria was still problematic in the southern United States. This U.S. agency was formed in order to limit the impact of malaria and other vector-borne diseases during World War II around military training bases. That is why, to this day, the CDC is headquartered in Atlanta, rather than Washington, DC.

West Nile Virus

Originating from the bird-biting mosquito Culex, West Nile Virus is the most common virus spread by mosquitoes in the continental United States. Since WNV is a virus, there is no vaccine or a specific treatment for it. The WNV affects the brain, where it impedes the central nervous system and causes inflammation in the brain tissue, known as encephalitis. However, according to the CDC, about 80 percent of those infected show no symptoms at all. About one out of 150 infected people develop a serious, sometimes fatal, illness. In 2002, the WNV outbreak in North America was the largest outbreak ever recorded, with 4,156 people infected[2].


At its peak in 2017, there were 542 cases of Zika in the United States. Only seven of those cases were contracted locally, while the majority of individuals with the virus contracted it while traveling. Even if someone is infected from a mosquito bite, symptoms are usually mild and almost never fatal. The real danger is posed to pregnant women, who pass the virus onto the fetus, frequently resulting in microcephaly. This virus gets its name from the Zika Forest in Uganda, where researchers think it originated in 1947, transmitted by Aedes mosquitoes.

Dengue Fever

With more than one-third of the world’s population living in areas at risk for infection, dengue virus is a leading cause of illness and death in the tropics and subtropics. Unlike other mosquito-borne viruses, Dengue has become more prevalent over the past decades. It is predominantly active in Southeast Asia and Latin America. In 2016, there were 3.34 million cases worldwide. As many as 400 million people are infected yearly.

Dengue is caused by any one of four related viruses transmitted by mosquitoes. There are not yet any vaccines to prevent infection with dengue virus and the most effective protective measures are those that prevent mosquito bites. When infected, early recognition and prompt supportive treatment can substantially lower the risk of medical complications and death.

Other common mosquito-borne viruses in other parts of the world include:

  • Yellow Fever: Endemic to tropical areas of Africa and Central and South America, Yellow Fever has been eliminated in other parts of the world, thanks to a very effective vaccine. The World Health Organization launched its Eliminate Yellow Fever Epidemics (EYE) Strategy in 2017 to help put an end to this disease.
  • Chikungunya: With symptoms of high fever and extreme joint pain, this mosquito-borne virus mostly occurs in Africa, Asia, and the Indian subcontinent.

Common mosquito-borne viruses that affect animals in the United States include:

  • Eastern Equine Encephalitis (EEE): Unfortunately, this mosquito-borne virus is typically fatal for horses.
  • Dog Heartworm (dirofilaria immitis): Mosquitoes can carry the larvae of roundworms and can transmit these larvae into dogs and cats (although dogs are much more susceptible to infection).

We know protecting your family and pets is your number one priority. Let Mosquito Squad fight the bite for you. Call (877) 332-2239 today for your free estimate!

[1] State of Connecticut Mosquito Management Program.

[2] Sejvar, James J. MD. The Ochsner Journal, 2003.