Risk factorsBy Mayo Clinic staff
Your 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.
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