2021 is turning out to be an especially harsh West Nile Virus (WNV) year in Arizona. Here in Pinal County, Public Health has 22 cases under surveillance. This is much higher than normal as the average number of cases since 2016 has been 5 cases per season.
Though thankfully no fatalities have been detected in Pinal County so far this year; there have been four deaths associated with West Nile Virus in the State of Arizona. The average age of cases in Arizona is 62; however, the age range for reported cases is 22 to 91 years.
West Nile Virus is the leading cause of mosquito-borne disease in the continental United States. It is most commonly spread to people by the bite of an infected mosquito. Cases of WNV occur during mosquito season, which starts in the summer and continues through fall. This season, with our monsoon rains occurring early and often, WNV activity is significant in Arizona.
While 60-70% of cases do not experience symptoms, all cases reported in Pinal County so far have been symptomatic. West Nile Virus can cause a mild illness that lasts for a few days or a more serious condition that affects the central nervous system. The risk of developing a more serious disease increases with age, immune status, and presence of comorbidities.
Arizona has an above-average incidence of neuroinvasive disease caused by West Nile Virus at greater than 0.75 cases per 100,000 population. If you have had a recent mosquito exposure and experience symptoms like fever, fatigue, joint pains, stiff neck, or altered mental state, please consult your healthcare provider.