The top two mosquito-borne illnesses affecting humans or domestic animals in Maine are Eastern Equine Encephalitis (EEE) and West Nile virus. Acquired mosquito-borne illness from international travel include such viruses as Dengue, Malaria, and Zika.

Eastern Equine Encephalitis (EEE)

  • Description:  Rare but serious disease that is caused by a virus. It can infect humans, horses, birds and other animals.
  • Signs & Symptoms:  Many people do not have obvious symptoms, in people that do develop the illness, symptoms range from mild-flu like illness to inflammation of the brain, coma and death.

  • Susceptibility: Present in Maine. People are at the highest risk of getting infected with eastern equine encephalitis between the months of May and October.

  • Prevalence:  Eastern half of the United States. Maine has two reported residents with EEE one in 2014 and 2015. One of the cases was fatal.

West Nile

  • Description:  Can cause disease in humans, birds or other mammals. Can be carried in birds, often when three or more dead birds are together.
  • Signs & Symptoms:  Many people have no obvious symptoms. If some does develop illness symptoms can include headache, high fever, altered mental state, tremors, convulsions and rarely paralysis.

  • Susceptibility:  Often during mosquito season, which starts in the summer and continues through the fall.

  • Prevalence:  Leading cause of mosquito-borne disease in the continental United States.


  • Description:  One of four related viruses transmitted to humans by the bite of an infected Aedes mosquito. About 40% of world population is at risk.
  • Signs & Symptoms:  It can include high fever, headache, severe pain behind the eyes, joint pain, muscle and bone pain, rash and mild bleeding
  • Susceptibility:  Majority of infections in US are acquired elsewhere by travelers or immigrants. There have been outbreaks in Hawaii, Texas and Florida. Endemic in at list 100 countries in Asia, the Pacific, the Americas, Africa and the Caribbean.
  • Prevalence:  Estimated 100 million cases of dengue worldwide each year 


  • Description:  Transmitted to people by mosquitoes.
  • Signs & Symptoms:  Most common symptoms are fever and joint pain. Other symptoms include headache. Muscle pain, joint swelling, or rash.  

  • Susceptibility:  Not currently found in Maine, they are present in large areas of the United States including Africa, Asia, Europe and the Caribbean.

  • Prevalence:  Reported cases are by U.S travelers returning from affected areas. In 2014, local transmission was identified in Florida, Puerto Rico, and the U.S. Virgin Islands.

Jamestown Canyon Virus

  • Description:  disease is an illness that are transmitted to people through the bite of an infected mosquito.
  • Signs & Symptoms:  Flu like symptoms

  • Susceptibility: Illness can occur in any age group

  • Prevalence:  People who work outside or participate in outdoor activities are at greater risk because of exposure to mosquitoes


  • Description:  Serious sometimes fatal disease.
  • Signs & Symptoms:  High fever, shaking chills and flu-like illness.

  • Susceptibility:  Majority are from travelers from sub-Saharan Africa and Southern Asia.

  • Prevalence:  1,500 cases of Maria are diagnosed in the United States a year.

Yellow Fever

  • Description:  Disease caused by a virus that is spread to people by the bite of an infected mosquito. Vaccination is available.
  • Signs & Symptoms:  Range from a fever with aches and pains to severe liver disease with bleeding and yellowing skin (jaundice).

  • Susceptibility: Not present in Maine but is typically found in the tropical and subtropical areas in Southern America and Africa.

  • Prevalence:  Typically rare in U. S travelers.


  • Description:  Zika is a virus spread mostly by the bite of an infected mosquito. These mosquitoes bite during the day and night. Zika can be passed from a pregnant woman to her fetus and can also be sexually transmitted.
  • Signs &  Symptoms:  Include fever, rash, headache, joint pain, red eyes, muscle pain.

  • Susceptibility: A Zika infection during pregnancy can cause birth defects other other problems such as miscarriage, and stillbirth.

  • Prevalence: There are have been no cases in the U.S in 2018, but Zika is found all over the world.

To learn more about Mosquito-borne diseases, visit the:  Maine Center for Disease Control & Prevention