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Bitten! Mosquito-Borne Illness and You

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  • Mosquito bites can transmit germs that cause illnesses. Learn about common diseases that some mosquitoes carry and spread among people. Use the links to MedlinePlus health topic pages to access reliable health information about the research, treatment, and prevention of mosquito-borne diseases.

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    • Bitten! Mosquito-Borne Disease & You

      Mosquitoes as Vectors

      Mosquitoes are insects that live all over the world. When a female mosquito lands on you and bites you, it drinks a small amount of your blood. Human blood contains essential nutrients mosquitoes need to produce their eggs. The bite usually causes an itchy bump and may produce an allergic reaction. Importantly, mosquitoes are also disease vectors. This means that they can carry germs picked up from an infected person or animal and spread the disease-causing germs when they bite others.

      Mosquito-Borne Diseases

      Common diseases that mosquitoes carry include chikungunya, dengue, malaria, West Nile virus, and Zika. Chikungunya, dengue, and Zika are caused by viruses, while malaria is caused by a single-celled parasite. These germs infect a person through a mosquito’s bite, and then use the human host to multiply. While this is happening, the human host often becomes sick. Chikungunya, dengue, and malaria are all common in tropical and subtropical regions of the world, but are rare in the United States.

      West Nile virus and Zika have become more common in the United States. Mainly infecting people during the summer months, West Nile virus is now the most prevalent mosquito-borne illness in the country, while limited Zika outbreaks have also occurred in recent years. However, it’s important to note that the mosquito species that carry each of these diseases live throughout the United States.

      Signs and Symptoms of West Nile Virus

      West Nile virus symptoms can include fever, headache, body aches, skin rashes, and swollen lymph nodes. Generally, infection causes very mild symptoms or no symptoms, at all. However, older people and people with weakened immune systems are at high risk for severe symptoms. It is important to pay attention to abnormal signs that may appear after getting a mosquito bite. If you think you may have contracted West Nile virus, talk to your doctor to get medical advice about your health and potential treatments.

      Prevention and Research

      Accurate, reliable health information is important for protecting you and your family from mosquito bites and the diseases they carry. There are a number of ways to help prevent mosquito bites: apply an effective insect repellent; cover up your arms, legs, and feet while outside; mosquito-proof your home by using screens on windows; avoid time outside when mosquitoes are most active – specifically dawn and dusk; and remove standing water where mosquitoes can breed.

      Mosquito-borne diseases are an ongoing threat to public health. Therefore, doctors and researchers continue to study these diseases to find and develop better methods to prevent and treat them.

      The National Library of Medicine offers trusted resources about mosquito-borne diseases and how to stay safe. Start with and find Trusted Health Information for You!

      This video was produced by the National Library of Medicine.

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Last Reviewed: May 7, 2021