West Nile Cases, Deaths Keep Breaking Records In Maricopa County

PHOENIX, AZ — Maricopa County continues to break records for the number of West Nile virus cases and deaths recorded this year. As of Friday, 1,300 cases had been recorded in the county, along with 90 deaths.

That's compared to three cases and only one death in 2020, according to Maricopa County Department of Public Health records.

Since around a month ago, on Nov. 19, the county has seen an additional 247 recorded cases of West Nile virus and 78 additional deaths, according to health department data.

With a particularly wet summer this year that followed an extraordinarily dry summer in 2020, conditions were perfect this year for West Nile virus to spread in Maricopa County.

Warmer-than-usual temperatures that extended through November and into early December kept the mosquito season going in the Valley when colder weather might have stopped it.

West Nile virus was first detected in Arizona in 2003, according to the Arizona Department of Public Health. People contract the disease when an infected mosquito bites them. West Nile is not transmitted through human-to-human contact.

Around 80 percent of people bitten by infected mosquitos never develop symptoms or even know they've infected. Slightly fewer than 20 percent might develop a flu-like illness, said Maricopa County Health Department Epizoologist, Melissa Kretschmer. Slightly fewer than 1 percent might develop a more severe illness that affects their brain and spinal cord.

Previous annual West Nile virus human case counts, according to Maricopa County Department of Public Health records:

• 2011: 50 cases and two deaths
• 2012: 98 cases and four deaths
• 2013: 52 cases six deaths
• 2014: 93 cases and 12 deaths
• 2015: 62 cases and two deaths
• 2016: 63 cases and five deaths
• 2017: 93 cases and six deaths
• 2018: 24 cases and six deaths
• 2019: 155 cases and 17 deaths
• 2020: Three cases and one death