Diseases that can be Transmitted by Mosquitoes

While mosquitoborne disease is not as common in Minnesota as it is in tropical climates, there are several diseases that may occur within the state. Minnesota residents who travel to other countries can also return with tropical diseases such as malaria or dengue.

• West Nile Virus (WNV)
  West Nile virus is a disease transmitted to people, horses, and birds. It is the most commonly reported mosquitoborne disease in Minnesota. Most people infected with West Nile virus show no symptoms or flu-like symptoms, but some (primarily elderly) have more severe illness. West Nile virus was found in Minnesota in 2002 and will remain a public health concern in the foreseeable future.
• La Crosse Encephalitis (LAC)
  La Crosse encephalitis is a viral disease that is transmitted by the Tree Hole mosquito. It has been responsible for an average of 4-5 cases each year in Minnesota, primarily involving severe illness in children.
• Jamestown Canyon Virus (JCV)
  Jamestown Canyon virus, which may be transmitted by several different species of mosquitoes throughout Minnesota, is a rarely reported cause of illness in humans. The virus is closely related to La Crosse virus although any age group may be affected.
• Western Equine Encephalitis (WEE)
  Western Equine Encephalitis is a disease transmitted to people, horses, and birds. It is caused by a virus that is transmitted by the same mosquito species that commonly transmits WNV in western Minnesota. In 1941, there was a large regional outbreak of WEE that affected nearly 800 Minnesotans. Since then, Minnesota has had infrequent and much smaller outbreaks of WEE (15 human cases in 1975, single cases in 1983 and 1999).
• Eastern Equine Encephalitis (EEE)
  Eastern equine encephalitis is a rare illness in humans and horses, and only a few cases are reported in the United States each year. Many people infected with EEE virus show no symptoms but some (primarily children) have severe illness. Although cases have been reported in horses, no human cases have been identified in Minnesota.
• St. Louis Encephalitis (SLE)
  CDC: Cases of St. Louis encephalitis are usually the result of unpredictable and intermittent localized epidemics. SLE has not been reported in Minnesota since the 1970’s.

Mosquitoborne Diseases Affecting Travelers

Minnesota residents who travel to other countries can return with mosquitoborne diseases such as malaria, dengue, chikungunya, yellow fever, and zika virus. Travelers should talk with their health care provider or visit a travel clinic before traveling to learn about what illnesses they may be at risk for and their associated symptoms. Medications used to prevent infection are available for malaria and vaccines are currently available for yellow fever. Avoidance of mosquito bites and use of mosquito repellent are recommended when traveling to affected areas. For more information on international travel, visit International Travel & Infectious Disease.

• Chikungunya
  CDC: Chikungunya virus is primarily found in Africa and Asia yet was found in 2013 for the first time in the Western Hemisphere. 
• Dengue
  CDC: Dengue fever is primarily a tropical disease and rarely occurs within the continental United States. Small outbreaks have occurred in the past in states such as Florida, Hawaii, and Texas.
• Malaria
  Malaria is a mosquitoborne disease caused by a parasite. It is found in many countries, including sub-Saharan Africa, South Asia, as well as Central and South America. Malaria is a serious illness and may be deadly but prevention methods are available. Most cases of malaria in the United States occur in travelers and immigrants.
• Yellow Fever
  CDC: Yellow fever virus is a rare tropical illness in Minnesota travelers with vaccination being one of the most important steps in prevention. 
• Zika Virus
  Zika virus is a concern in many parts of the world. While most people who become infected with Zika virus have mild symptoms or no illness at all, the virus has been linked to serious health conditions, including Zika congenital syndrome in babies.