Risk factors

Most cases of West Nile virus in the United States occur June through September. Cases have been reported in all 48 lower states.

Risk of serious infection

Even if you're infected, your risk of developing a serious West Nile virus-related illness is very small. Less than 1% 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. Being older puts you at higher risk.
• Certain medical conditions. Certain diseases, such as cancer, diabetes, high blood pressure (hypertension) and kidney disease, increase your risk. So does receiving an organ transplant.