West Nile Virus-Infected Mosquitoes Are Increasing In Arizona

By Sherah Janay Ndjongo

September 27, 2023

Mosquito on a leaf
Photo: Getty Images

Despite the scorching and parched summer conditions, an alarming surge in West Nile virus-infected mosquitoes has gripped the entire state of Arizona, especially around Phoenix.

Spearheading the battle against this growing threat is the Maricopa County Environmental Services Department, responsible for capturing and scrutinizing mosquitoes for the West Nile virus. In a single night, a whopping 89,000 mosquitoes were ensnared in a trap nestled within a Mesa neighborhood, which draws attention to the severity of the situation.

Maricopa County’s lab division manager John Townsend shed light on their meticulous process, involving the deployment of over 900 CO2 traps to lure and transport the mosquitoes into the lab. Inside, swarms of these tiny culprits are meticulously examined. Townsend noted the accelerated onset of the mosquito season, with May and June witnessing a significant uptick in positive cases.

However, the relentless dry heat curtailed mosquito lifespans, from the usual four to six weeks down to a mere three weeks, reducing their opportunities to transmit the virus by biting infected birds. This year, over 150 mosquito samples have tested positive, dwarfing the 62 cases from the previous year, with the virus's reach extending to unexpected corners of the state.

Townsend stressed the importance of pinpointing affected areas to facilitate targeted intervention and locate breeding sites. With the arrival of cooler weather, he anticipates a decline in both positive samples and cases.

Despite the current concerns, the situation pales in comparison to the 2021 West Nile virus outbreak in Maricopa County, which saw its peak in September and October, posing a more stubborn challenge.

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