Dr. Crystal Hepp

Dr. Crystal Hepp, an assistant professor at NAU’s School of Informatics, Computing, and Cyber Systems, was the lead researcher in a 2019 study that analyzed the genetic material of West Nile Virus directly from mosquitos collected mainly in Maricopa County. 

As Scottsdale and the rest of the nation struggle with the ongoing menace of COVID-19, another public health danger is becoming a bigger threat here.

West Nile virus – long considered a permanent public health threat in the Valley and Arizona – has become particularly menacing as a result of last month’s heavy rains. 

The mosquito-borne threat already has hit home in parts of the Valley. In Ahwatukee, two residents between the ages of 40 and 60 from different households were hospitalized. While one has been discharged, the other has been moved to a rehab facility.

TV Channel 3 broadcast a report on a Peoria man who is in the hospital paralyzed by the disease and the Maricopa County Department of Public Health announced that West Nile Virus has claimed its first life of the season.

“We all need to do our part to protect ourselves, our family and our neighborhoods from mosquito-borne diseases,” said Dr. Rebecca Sunenshine, medical director of the Disease Control Division at Maricopa County Department of Public Health. “With so much rain this summer, we all need to stay mindful of eliminating standing water where mosquitos can breed, like pet dishes, potted plants, and even toys.”

She reported that 36 human cases of West Nile Virus have been reported so far this year – a sharp increase over the three cases reported last year that resulted in one death.

“This is a significant increase in cases,” the department said. “The individual who died was an older adult who also had other health conditions. While adults over 60 and those with chronic health conditions are most at risk for serious complications of West Nile virus, young healthy individuals can also get severe disease.

The Maricopa County Environmental Services Department, which conducts aggressive year-round mosquito surveillance and abatement programs, reported a nearly 400 percent increase in positive West Nile virus mosquito samples compared to all of last year.

The Arizona Department of Health Services last Friday reported two deaths statewide so far this year and a total 451 cases of severe illness.

Residents of Ahwatukee Lakes have been particularly vocal here in expressing concern about the half-filled lakes providing a more potent breeding ground for infected mosquitoes.

“The large body of untreated standing water by Lakeside…continues to place all of us at risk for infectious diseases such as West Nile Virus,” resident Jayne Russell wrote.

West Nile virus can cause severe disease, though only about one in five of those infected will develop any symptoms at all. 

Those who do develop symptoms usually experience a flu-like illness including fever, headache, body aches and muscle weakness. About one in 150 victims infected can develop encephalitis or meningitis, an inflammation of the brain or of the spinal cord. 

“This more severe form of the disease can present with headache, neck stiffness, vision loss, paralysis and other neurologic symptoms,” the department said. “These severe cases can lead to very prolonged illness, permanent paralysis or death. Those who are over 60 years old, have underlying medical conditions or have depressed immune systems are at higher risk for the more severe form of West Nile Virus.”

Animals, particularly horses, also can be sickened by infected mosquitoes.

Originally isolated in 1937 in the West Nile district of Uganda, Africa, the first Arizona case appeared in 2003, four years after it first emerged in the United States, most likely from bird migrations. 

A study two years ago by Northern Arizona University and the Translational Genomics Research Institute said  NAU-TGen study said Arizona’s moderate temperatures allow the West Nile Virus to survive throughout the winter.

It usually is active in the summer and fall, dissipating when temperatures reach freezing, something that rarely happens in Maricopa County.

“This is the first genomic evidence of local over-wintering by WNV strains over the course of several years in Arizona,” said Dr. David Engelthaler, co-director of TGen’s Flagstaff-based Pathogen and Microbiome Division, TGen North, and the study’s senior author. “These findings will allow public health officials to better track the virus, allowing for more targeted vector control and public education campaigns.”

West Nile Virus samples for the study were collected from mosquitoes trapped weekly at 787 sites throughout the Phoenix metro area by the Maricopa County Environmental Services Department Vector Control Division.

“The protocol we created for this study can now be incorporated into routine public health surveillance activities, allowing for better tracking of local viral hotspots, changes in local viral populations and detection of the emergence of new strains of WNV,” Hepp said. 

“We are currently conducting WNV surveillance across western states to better understand how permanent Arizona viral populations may be a source for continual reintroductions to other regions and other states,” she added.

Maricopa County conducts fogging operations to combat mosquitos and its most recent map shows where they have been launched. Go to  maricopa.maps.arcgis.com/apps/webappviewer/index.html?id=c00b3ecbb3344ca2930a30b978184ddd. A calendar of fogging operations is at maricopa.gov/calendar.aspx?CID=51.

For other information about West Nile Virus: maricopa.gov/2423/Fight-the-Bite.