In the midst of the COVID-19 pandemic, another virus has caused havoc in one Arizona county, resulting in a record-breaking outbreak that caused the death of 101 people, as per a study released by Arizona health officials. This virus is West Nile, which is spread by mosquitoes that primarily become infected after biting infected birds. Although eight out of ten infected people remain asymptomatic, the unlucky ones may experience fever, joint pains, vomiting, diarrhea, or rash. However, a small percentage of symptomatic cases may lead to serious, life-threatening neuroinvasive cases like encephalitis or meningitis.
West Nile Virus (WNV) was discovered in the US in 1999 and was first detected in Arizona in 2003. Since then, there have been around 100 cases in the state every year, with Maricopa County recording most of them. The outbreak record was set in 2004, wherein the state recorded 391 cases, with 355 from Maricopa. However, in the summer of 2021, Maricopa’s WNV outbreak totaled to a record-breaking 1,487 symptomatic cases, the largest ever recorded from any county in the country.
The huge number of neuroinvasive cases in the outbreak suggests that a massive number of cases went unrecorded. According to previous estimates, for every one neuroinvasive case, there are between 30 to 70 non-neuroinvasive symptomatic cases. That would put the true case total between 28,700 and 67,000 in the county, which has a population of around 4.5 million.
It’s unclear what could have caused the massive outbreak, but Arizona health officials speculate that it could be related to a confluence of factors like increased rain, extended WNV season in Arizona caused by rising temperatures, recent population growth, housing development in Maricopa, and changes in health care-seeking behavior during the COVID-19 pandemic. Although both viruses are here to stay, Arizona officials are working on ways to improve responses by identifying data thresholds for increased public and provider messaging on prevention, diagnosis, and testing, and timely and coordinated mosquito and human case surveillance to identify outbreaks and guide prevention efforts.
