TGen, NAU Researchers Say West Nile Virus a Permanent Part of Arizona’s Ecosystem

PHOENIX – Every day is a challenge for Bruce Gran, 52, who was diagnosed with West Nile virus seven years ago.

“From Day 1, it’s been a migraine-caliber headache,” the Tucson resident said. “My short term-memory is terrible. I’m not old enough to be having the effects that I have. ”

Gran is one of the hundreds of Arizonans who have been infected by West Nile since the mosquito-borne disease was discovered in the state in 2003.

Sixteen years later, the virus is here to stay, according to a study from Northern Arizona University in Flagstaff and the Translational Genomics Research Institute in Phoenix. And the southern half of Arizona appears to be an ongoing source of West Nile in neighboring states.

There are several types of mosquitoes in Arizona, but the two main ones that carry West Nile – Culex tarsalis and Culex quinquefasciatus – stay year-round due to central Arizona’s mild winters, TGEN associate professor David Engelthaler said.

“We could actually find the remnants of the original strain that affected the U.S. in New York and has marched its way across the U.S.,” he said. “There’s another evolving strain that has been evolving in Texas and is now a permanent resident in Maricopa County as well.”

West Nile symptoms can vary, making the illness difficult for doctors to diagnose. Most cases cause mild flu-like symptoms; others end in death.

Some patients, like Gran, can experience a life-changing neuroinvasive illness.

“The harder you push to do things, the harder it (the virus) pushes back,” he said.

The disease has robbed the auto technician of feeling in three of his fingers, so he tapes his hands every day.

“I can’t feel anything,” Gran said. “They’re numb. But yet, when I bend my joints past a certain point, it feels like someone is driving a spike through them.”

West Nile also is the reason for Gran’s severe headaches.

“It’s a seven or an eight on the pain scale” of 10, Gran said. “It gets worse, but it never goes below that.”

After the diagnosis, he began to experience short-term memory loss.

“I can watch a sitcom tonight and watch it again tomorrow or a couple days later and not know I watched it,” Gran said.

His wife, Christine Gran, said the disease has drastically impacted their family.

“Ask my children, my three sons,” she said. “They really don’t have their dad. It’s just that debilitating.”

Many West Nile patients experience symptoms so severe they’re unable to work, but even for those who can, daily tasks can be agonizing.

“There were days for years where he would go to work for a couple hours and just be done, “ Christine said. “He only makes it until about 2 in the afternoon and then everything gets excruciating. His whole body aches and he just needs to come home and sit. We’ve lost so many days of work.”

For the days that Gran can work on cars, he needs a list to remember what jobs need to be completed.

Asked how the disease has impacted his social life, Gran responded “What social life?”

The Business of Mosquito Trapping

Mosquito traps are filled with dry ice and attached to a net and a battery-operated fan, which attracts and traps the insects. They are then taken to the Maricopa County Vector Control lab for examination to track patterns of mosquitoes and the West Nile virus. (Photo by Sarah Donahue/Cronkite News)

After the first West Nile virus case appeared in Arizona in 2003, Maricopa County expanded its vector-control program to study and control the mosquito population in metro Phoenix. Since the following year, the number of cases in Arizona has steadily declined, to 27 in 2018.

County field inspector Dan Armijo helps place mosquito traps all over Phoenix. Vector Control sets out more than 800 traps daily.

On a recent afternoon, Armijo pulled up to a small park in a west-side neighborhood, hopped out of his truck and filled a trap with dry ice from a cooler in the back.

Dry ice is used because it evaporates to release a cloud of carbon dioxide – something mosquitoes are attracted to, Armijo said. It’s the females that bite people and other mammals to draw blood to incubate their eggs.

Armijo said mosquitoes are drawn to Arizona because, despite the dry climate, the state actually has a lot of stagnant water – puddles, water fountains, neglected swimming pools.

According to the Arizona Department of Health Services, Maricopa and Pima counties have the highest reported cases of West Nile virus in Arizona. (Photo by Sarah Donahue/Cronkite News)

Armijo hung the trap on a tree branch near a fountain in the park.

“We’ll set this trap overnight,” he said. “We’ll come back and pick it up in the morning.”

The traps are individually barcoded and numbered so the inspectors can keep track of what they find. The number of mosquitoes the traps catch varies depending on weather conditions and the amount of stagnant water nearby. The captured mosquitoes are separated by gender because only the females bite and carry West Nile, Armijo said.

“If even one mosquito comes back with a trace of the virus strand, we’ll fog the whole square mile,” Armijo said.

Here to Stay

Engelthaler said the West Nile study was heavily focused on Maricopa County because the virus is mostly found in the southern half of the state.

Because the disease is a permanent resident of Arizona’s ecosystem, the strains could affect adjacent states, Engelthaler said.

“The strands that show up in Yuma and Southern California seem to be either annually or regularly coming out of Maricopa County,” he said. “Maricopa County is kind of acting as a source for neighboring areas to get West Nile virus on a regular basis.”

Steve Young, a vector technologist at Maricopa County Vector Control, examines mosquitoes to determine if they carry the West Nile Virus, the most common mosquito-borne illness in Arizona. (Photo by Sarah Donahue/Cronkite News)

Engelthaler believes the study results can help Maricopa County control the spread of West Nile and raise awareness about the virus.

“We do think that this information is going to give more precise and targeted control efforts,” Engelthaler said.

Maricopa residents can file a vector complaint online. The county will send inspectors to the area to set up traps.

It’s not just you. The mosquitoes really are worse this year

Can’t leave the house without getting bitten? Legs swollen from scratching? Welcome to the crowd. Because yes. The mosquitoes are worse this year.

Why? There’s a new type of mosquito roaming the southern United States. You might have heard of it — it’s the aedes mosquito — and it first showed up in 2010. It’s even present in areas experiencing drought like the southwest. It’s way more vicious than the most common mosquito, known as the house mosquito, or the culex.

(Maps credit to Center for Disease Control).

Unlike the culex, aedes mosquitoes bite during the day. And they go for the legs and ankles, instead of buzzing around your ears, so you can’t hear them coming.

“They’re sneaky biters,” said Yessenia Avilez, an inspector for the Greater L.A. County Vector Control District.

It’s Avilez’s job to find and destroy the aedes mosquito. And on a hot day in August, I went along for the kill.


It’s 8 a.m., and Avilez and her mosquito-killing partner, Faiza Haider, are parking their big white truck on a steep street in Echo Park, a neighborhood in Los Angeles.

It’s their second appointment of the day, and they have at least six more to go after this. Vector Control inspectors are busiest in the summer, when the heat speeds up the aedes’ reproductive cycle. That means the invasive mosquito infestation could get worse in the future, as temperatures rise.

Vector control inspectors Yessenia Avilez and Faiza Haider see if they caught a mosquito in the net inside their aspirator. (Photo by Emily Guerin/LAist)

Both women are petite, and their matching blue shirts and work pants look a bit too big for them. They both wear visors with an embroidered mosquito on the front, and their shiny Vector Control badges. The only thing personalized about their outfits are their tiny sparkly earrings.

(Sidenote: Avilez and Haider both starred in Vector Control’s awesome “Mosquito Rap” video PSA last year. It’s fun and catchy and you should watch it below. It was written by Metamorphosis and is part of the Mosquito S.W.A.T lab. )

-Video by GLACVCD

Avilez and Haider bring a few things to every appointment: a big black tool box — they call it “Fat Max” — that contains tupperware to bring mosquitoes and larvae back to the lab, their flashlights, pamphlets to give to residents and their mosquito catching vacuum.

They call it the “aspirator,” but it’s really just a leaf blower with the motor reversed, so it sucks air (and bugs) in instead of blowing out.


Once they get into the back yard, Haider and Avilez fan out.

“We’re looking for standing water,” Haider said. “Something as small as a bottle cap can breed mosquitoes.”

Culex prefer to lay their eggs in big sources of water, like swimming pools, but the aedes mosquitoes hardly need any water at all

That’s one key difference between the invasive aedes and native culex mosquitoes. Culex prefer to lay their eggs in big sources of water, like swimming pools, but the aedes mosquitoes hardly need any water at all. Both mosquitoes, however, can carry diseases: culex has successfully transmitted West Nile to six people in L.A. County already this year, while aedes can transmit Zika virus and dengue fever, although that hasn’t happened yet.

The women pick up potted plants, checking to see if the trays underneath are holding stagnant water. They peer into bamboo thickets, looking for places where water collects. They inspect doggy dishes, looking for larvae. And they take out their flashlights to check out empty buckets and pots, looking for the thin white calcium line where water used to be.

“The invasive mosquitoes likes to deposit its eggs right above the water mark,” Haider said. And the eggs can lie dormant for years, just waiting for the pot or bucket to be refilled again. That’s why when she and Avilez find a line of eggs in a dry pot, they’ll take it back to their lab and destroy it, or have the resident give it a good scrub with soap or bleach.

Jane Stephens Rosenthal is scratching her arms while she watches. She’s lived here for five years and called Vector Control because the mosquitoes have never been this bad.

“I was out here on a call at 9:30 a.m. for half an hour, and my legs were totally bitten,” she said. “They’re just nasty.”


After hunting around for 15 minutes, the women don’t find any standing water, or dried eggs. So they decide to try to catch a mosquito, to make sure it is, in fact, the invasive aedes that’s been bothering Stephens Rosenthal.

Haider takes out the aspirator and holds it up like a squirt gun, jabbing it towards a mosquito buzzing near the back of the yard. She looks like one of the Ghostbusters.

If she catches one, she’ll slam the lid on the tube of the leaf blower and check to see what kind of mosquito it is. But this time, the little bugger got away.

As the women turn to leave, Stephens Rosenthal offers a tip: there could be an uncovered rain barrel at the neighbor’s house.


It’s not uncommon for mosquitoes to breed at one house and fly over the fence to bite the people next door.

“This mosquito doesn’t travel very far,” Avilez said. “It stays very close by to where it just hatched.”

So the women head one house down and ring the doorbell. No one is home. But through the fence they can see, beneath the deck, a giant, uncovered rain barrel. They poke their flashlights through the fence, shining it at the hole.

“That’s a point of entry,” Avilez said, “so mosquitoes can just fly in, deposit their eggs and fly out. It’s a perfect environment. It’s shaded, there’s people, there’s food.”

It must be frustrating, I say, to be looking at a potential source of mosquitoes, but not be able to do anything about it. Ideally, the inspectors would treat the rain barrel with larvicide right away.

But Avilez shrugs. It’s part of the job. So they tape a note on the door (tape and pamphlets emerge from Fat Max), and they’ll come back in three days if the homeowner doesn’t call back.

It’s illegal, at least in California, to ignore a source of mosquitoes on your property, and you can be fined up to $1,000 a day for refusing to fix the problem.