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Mosquito-Borne Diseases



There are several mosquito-borne diseases of concern in Delaware: Chikungunya, West Nile Virus, Eastern Equine Encephalitis, and Canine Heartworm Disease, and a possible newcomer, Zika, for which the state’s awareness is growing.

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Learn how you can control mosquitoes in your own backyard. (Video)

Zika Virus

Zika virus is a pathogen transmitted by mosquitoes that is now largely threatening Central and South America, the Caribbean islands, and the southeastern U.S. Symptoms include fever, rash, joint pain, headaches, muscle aches and/or conjunctivitis. Rarely fatal, the illness is usually mild with symptoms lasting several days to a week. What distinguishes the Zika virus from other mosquito-borne illnesses is the effect it seems to have on pregnancy. Zika can spread from a pregnant mother to her baby, and that infection may be linked to birth defects such as microcephaly.

The mosquito species capable of transmitting this disease are the Yellow Fever Mosquito (Aedes aegypti) and the Asian Tiger Mosquito (Aedes albopictus). Both species lay their eggs largely in man-made containers, such as tires, buckets, corrugated rain spouts, etc. Traditional mosquito control methods of truck-mounted and aerial sprays are limited in controlling these mosquitoes, since they are often active during daylight hours.

Reducing mosquito populations around the home via removal of containers that hold water and thus become prime mosquito habitat is one of the key strategies for preventing mosquito bites and the possible transmission of Zika virus.

More Information

From the Delaware Division of Public Health

Zika Virus Fact Sheet

Chikungunya Virus

Chikungunya virus (CHIKV) is a pathogen transmitted by mosquitoes that is now threatening the United States. Although rarely fatal, the symptoms include debilitating joint pain and can persist for several weeks. In 2014, Florida, Puerto Rico, and the U.S. Virgin Islands recorded their first locally-acquired cases. According to the Centers for Disease Control, in 2018 only 1 travel-related case of CHICKV was reported in Delaware. As of October 3, 2019, no local or travel-related cases of CHIKV have been reported in Delaware.

The mosquito species that transmit this disease are the Yellow Fever Mosquito (Aedes aegypti) and the Asian Tiger Mosquito (Aedes albopictus). Both species lay their eggs in man-made containers, such as tires and buckets. Traditional mosquito control methods of truck-mounted and aerial sprays are somewhat ineffective in controlling these mosquitoes. Removal of containers that hold water and yard sanitation are key strategies for preventing Chikungunya.

More Information

From the Centers for Disease Control and Prevention

From the American Mosquito Control Association

West Nile Virus

West Nile virus (WNV) is a virus transmitted by mosquitoes. While there is a vaccine available for horses, there is no human vaccine for WNV. The best way to reduce your risk of WNV is to protect yourself from mosquito bites.

The Mosquito Control Section reminds residents and visitors to protect themselves from mosquito bites and mosquito-borne disease by avoiding mosquito activity when possible, dressing in long sleeves and long pants, and properly applying mosquito repellent.

More Information

West Nile Virus in Delaware brochure

From the Centers for Disease Control and Prevention

From the Delaware Division of Public Health

Eastern Equine Encephalitis

Eastern Equine Encephalitis (EEE) is transmitted to horses and humans by mosquitoes. Like West Nile virus, there is a EEE vaccine available for horses, but not for humans. Fortunately, human cases of EEE in Delaware are rare. The last recorded human case of EEE in Delaware occurred in 1979.

More Information

From the Centers for Disease Control and Prevention

Heartworm Disease

Canine heartworm, a disease fatal to dogs, is circulated within the dog population by mosquitoes. The Delaware Mosquito Control Section does not monitor heartworm levels in the mosquito population. Dog owners are encouraged to protect their pets from heartworm by administering preventative medications year-round.

More Information

From the American Heartworm Society

Additional Resources

The American Mosquito Control Association has created short, educational videos about mosquito-borne diseases and how these diseases have affected the US population.

Mosquito Control and Why It’s Important to You

One Mosquito, One Bite




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