Diseases Caused by Mosquitoes

Imagine coming back from your dream tropical vacation only to become seriously ill. Questions you and your family may ask include: Why am I so sick? What caused this illness? Did I pick something up while we were on vacation? Do I need to see a doctor?

In the U.S., we tend to associate mosquitoes with their pesky bites and nothing more. But mosquitoes can be deadly. At a minimum, they can make you very sick. Each year, mosquitoes are responsible for spreading serious illnesses to people around the globe. More than 1 million of these people die.

To protect yourself and your family from mosquito-borne diseases, you must first familiarize yourself with these diseases. Dengue and malaria are the most widely known, yet there are countless others that make the mosquito the most dangerous animal on the planet.

Dengue Fever

Primarily a disease of the tropics and subtropics, dengue fever is transmitted by mosquitoes that thrive in that climate. Mosquitoes and humans pass the virus back and forth. Dengue may soon pass malaria as the most harmful mosquito-borne viral disease that affects humans.

The spectrum of illness from this virus spans flu-like symptoms to fatal hemorrhagic fever. There are four types of this fever and, once recovered, victims develop immunity to the particular strain they were infected with. The danger of serious complications increases with a second infection of another type, and the more serious dengue hemorrhagic fever may occur.

Symptoms of dengue fever can include any of the following:

  • sudden, high fever
  • headaches severe in nature
  • severe pain behind the eyes
  • joint pain
  • bone and/or muscle pain
  • abdominal pain
  • persistent vomiting
  • vomiting blood
  • black or tarry excrement
  • rash
  • bleeding from nose or gums or bruise easily
  • low white blood count
  • drowsiness
  • breathing difficulty

As fever decreases during the 3-7 days following onset, other symptoms may appear. No specific medicinal treatment is available. Analgesics with acetaminophen may be used as pain relievers. Rest and plenty of fluids to avoid dehydration are recommended. Drugs that contain ibuprofen, Naproxen, or aspirin should be avoided.

Early diagnosis and hospitalization are required to manage the disease most effectively.

Yellow Fever

Another mosquito transmitted illness that is also found in tropical areas is called Yellow Fever. It starts out with common flu-like symptoms such as aches, fever and nausea. Despite the fact that these symptoms eventually subside, the second phase of the illness comes weeks later and can cause liver damage. As a result, victims become jaundiced and death is often the end result.

Yellow fever is spread by the Aedes Aegypti mosquito species and occurs most frequently in Africa and South America.

West Nile Virus

West Nile Virus is a growing concern in North America. Outbreaks spread rapidly beginning when mosquitoes feed on birds infected with the virus. These mosquitoes then pass the virus to their human hosts. West Nile Virus is not transmitted from person to person.

Most infected people do not become ill, with less than 1% developing severe illness. Those who do get sick often have existing health problems and high blood pressure. Onset starts three days to two weeks following contact and symptoms include: fever, stiffness, feeling uncoordinated and confused. Infants, the elderly and AIDS sufferers are at higher risk of showing symptoms of West Nile fever.

While there is no known treatment for West Nile Virus, most cases clear up on their own. Although in some cases the virus may persist in the kidneys, brain, spine and blood for months or even years after infection. What actually remains are called antibodies and “memory” white blood cells that provide protection from the virus in the future. However, these victims can experience permanent symptoms such as weakness, tiredness or memory loss.


As perhaps the world’s oldest mosquito-borne disease, malaria is so well-entrenched in some regions that up to 500 million cases are still reported annually. And more than 1 million die, most of them children in tropical and sub-tropical nations. The disease is carried by the Anopheles species.

Symptoms of this disease include: chills, high fever, headache, vomiting and diarrhea. In serious cases, malaria can cause multiple organs within the body to fail. This can result in seizures, comas, heart failure or death. Antimalarial drugs have been available for over 50 years and scientists are working on more.


Encephalitis is an arbovirus that attacks the central nervous system and causes brain inflammation. An arbovirus is maintained when mosquitoes or other blood feeding arthropods transmit it to susceptible vertebrate hosts. The virus can survive a complex life cycle inside nonhuman hosts, but when human contact or ecological change interfere with the cycle, the virus escapes. Humans and domestic animals may display a clinical illness. They do not, however, normally produce enough viremia to make a contribution to the transmission cycle.

The five most common types of encephalitis are:

  • Eastern Equine Encephalitis
  • Japanese Encephalitis
  • LaCrosse Encephalitis
  • St. Louis Encephalitis
  • Western Equine Encephalitis

Most human infections result in flu-like symptoms, or are asymptomatic. But when the infection leads to encephalitis, permanent neurological disorders or death can occur. The most common symptoms are:

  • High fever
  • Headache
  • Confusion
  • Fatigue
  • Stiffed neck

Treatment is available for brain swelling and loss of brain activity that controls breathing, but there is no anti-viral medication for encephalitis. Complications, like bacterial pneumonia, can develop, but are treatable. Research is being conducted to survey, diagnose and control arboviral encephalitides.

Chikungunya Virus

The Chikungunya virus is another harmful illness that is transmitted by mosquito bites. This virus is commonly found in Asian countries. Its symptoms are initially similar to dengue fever. However, it is followed by a second phase of illness that causes pain in the joints. This pain can last anywhere from a few weeks to a few years, and it can be debilitating. Currently there is no cure for this virus. Thankfully, fatalities from this virus are rare.

Heartworms in Pets

If you have pets, particularly dogs, mosquitoes can make them sick, too. Dogs are susceptible to heart worms, which is spread by mosquitoes. You can help prevent heart worms by taking your dog for regular checkups with a veterinarian. Heart worm medication can be prescribed for the prevention of heart worms.


Learn more about the parts of the world with the worst mosquito problems, the latest developments in mosquito control, plus pick up a few mosquito prevention techniques to protect your family from these dangerous pests.