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Risk factors
By Mayo Clinic staffYour overall risk of getting West Nile virus depends on these factors:
- Time of year. The majority of cases in the United States have occurred between the months of July and September.
- Geographic region. West Nile virus has been reported in most of the United States, but Midwestern and Southern states have recently had the highest incidence rates.
- Time spent outside. If you work or spend time outdoors, you have a greater chance of being bitten by an infected mosquito.
Risk of serious infection
Even if you're infected, your risk of developing a serious West Nile virus-related illness is extremely small — less than 1 percent of people who are infected become severely ill. And most people who do become sick recover fully. You're more likely to develop a severe or fatal infection based on:
- Age. Adults older than age 50 are at higher risk of infection.
- Health. Those who have a weakened immune system, such as after receiving an organ transplant with anti-rejection medication, are at greater risk of infection.
References
- West Nile virus: Questions and answers. Centers for Disease Control and Prevention. http://www.cdc.gov/ncidod/dvbid/westnile/qa/symptoms.htm. Accessed Sept. 5, 2012.
- West Nile virus: Fact sheet. Centers for Disease Control and Prevention. http://www.cdc.gov/ncidod/dvbid/westnile/wnv_factSheet.htm. Accessed Sept. 5, 2012.
- Petersen LR. Clinical manifestations and diagnosis of West Nile virus infection. http://www.uptodate.com/ index. Accessed Sept. 5, 2012.
- Ferri FF. Ferri's Clinical Advisor 2013: 5 Books in 1. Philadelphia, Pa.: Mosby Elsevier; 2012. http://www.mdconsult.com/books/about.do?eid=4-u1.0-B978-0-323-08373-7..00002-9&isbn=978-0-323-08373-7&about=true&uniqId=343863096-23. Accessed Sept. 6, 2012.
- West Nile virus. National Institute of Allergy and Infectious Diseases. http://www.niaid.nih.gov/topics/westnile/understanding/pages/what.aspx. Sept. 6, 2012.
- Centers for Disease Control and Prevention, et al. West Nile virus and other arborviral diseases — United States, 2011. MMWR. 2012;61:510. http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6127a3.htm?s_cid=mm6127a3_w. Accessed Sept. 5, 2012.
- Petersen LR. Treatment and prevention of West Nile virus infection. http://www.uptodate.com/ index. Accessed Sept. 5, 2012.
- Updated information regarding insect repellants. Centers for Disease Control and Prevention. http://www.cdc.gov/ncidod/dvbid/westnile/RepellentUpdates.htm. Accessed Sept. 7, 2012.
- Anderson CF (expert opinion). Mayo Clinic, Rochester, Minn. Sept. 10, 2012.
- Mahoney KR (expert opinion). Food and Drug Administration, Rockville, Md. Jan. 10, 2011.
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