Mosquitoes are active all year round in Arizona, but they are most abundant in the state from March to October. More than 40 mosquito species can be found in Arizona, most of which are not pests. Some mosquito species in Arizona are capable of transmitting diseases to humans, while others are merely a nuisance. The mosquito-borne diseases that occur in Arizona include the West Nile virus, western equine encephalitis, and St. Louis encephalitis.
Aedes aegypti is an invasive mosquito species that transmits chikungunya, dengue fever, yellow fever, and the Zika virus in many regions around the world. With the exception of yellow fever, all of the above diseases have been locally transmitted by Aedes aegypti in several southern US states within the last decade, but not yet in Arizona. Aedes aegypti, or the “yellow fever mosquito,” as the species is more commonly known, is an invasive species that was first discovered in Arizona only recently, and experts say that it is only a matter of time before this species starts to spread tropical diseases in the state.
Currently, the title of the most dangerous mosquito species in Arizona belongs to the Culex genus, specifically Culex quinquefasciatus and C. tarsalis, or the “southern house mosquito,” and the “western encephalitis mosquito,” respectively. These two species are considered dangerous because they both spread the West Nile virus and St. Louis encephalitis in Arizona, and both of these diseases are becoming more common in southern Arizona, particularly in Phoenix.
In rare cases, the West Nile virus and St. Louis encephalitis can both advance to encephalitic conditions that ultimately result in coma or death. Unfortunately, the West Nile virus has become a permanent part of Arizona’s ecosystem. According to the Centers for Disease Control and Prevention, 174 people contracted the West Nile virus in Arizona during the 2019 year, 18 of whom ultimately died as a result. This made Arizona the state with the highest number of confirmed West Nile cases in the country. Due to the mosquito threat in Arizona, residents should always apply repellent products that contain DEET, picaridin or another EPA approved mosquito repellent before stepping outdoors.
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