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This week on The Hot Spot:

West Nile Virus (WNV) in Maricopa County

The Maricopa County Public Health Department confirmed this week that as of 8/9/2019 there have been 107 confirmed cases of West Nile Virus (click here for an in-depth description of WNV) within Maricopa County with seven WNV related deaths. While not unusual to have cases of WNV in Arizona, this year’s cases have already surpassed the 24 cases seen in 2018. West Nile Virus is the leading cause of mosquito-borne infection within the United States and there are no vaccines currently available.

Arizona is host to many different mosquito species each with the potential to be a host to a number of Arboviruses. Currently, Arizona has had confirmed cases of the big five vector-borne Arboviruses: Dengue, Chikungunya, Zika, West Nile Virus and St. Louis Encephalitis within the last five years. West Nile was first confirmed in the state back in 2004 and is seen in all 48 continental US states.

Only about 20% of all infected individuals will present with symptoms which include: fever, rash, widespread pain, headache, joint aches, vomiting, and diarrhea. The vast majority of people will recover quickly with little to no lasting effects. However, about 1 in 150 people will develop a severe neurological illness such as encephalitis or meningitis. 


The only known prevention for arboviruses is the avoidance of mosquito bites and the management of mosquito breeding grounds. Make sure to avoid standing water such as puddles, birdbaths, or canals. If outside, try to wear long sleeves or pants (and yes, I am aware we live in Arizona and it is ridiculously hot), burn mosquito repellant candles/torches, and be sure to wear plenty of bug repellent.

A Review: What are Vector-Borne Diseases?

Vector-borne diseases account for approximately  17% of all infectious diseases and include illnesses such as Malaria, Dengue, Zika and West Nile. Vector-Borne Diseases are diseases spread by vectors such as mosquitoes, ticks, and other living organisms, which ingest a pathogen from one food source and then transfer the pathogen to another organism while feeding. The most well-known vector-borne disease is Malaria, which accounts for over 600,000 deaths annually. Globally there are over 1 billion cases of vector-borne diseases a year with a million deaths.

The spread and transmission of such diseases depend on many different factors such as climate, environment and human-vector interactions. The increase in global tourism and trade has had an immense impact on the increased prevalence of these diseases in previously uninfected areas.


Maricopa County Public Health Department (2019) West Nile Virus. Maricopa County Public Health Department website: https://www.maricopa.gov/1746/West-Nile-Virus

Centers for Disease Control and Prevention (2018) West Nile Virus. Centers for Disease Control and Prevention website: https://www.cdc.gov/westnile/index.html

World Health Organization. (2018) Vector-Borne Diseases. Media Center. World Health Organization website: https://www.who.int/news-room/fact-sheets/detail/west-nile-virus