An older East Valley man died earlier this month after contracting the West Nile virus, the Maricopa County Department of Public Health confirmed this week.
The death marks the second West Nile-related death this year and the second East Valley victim. An elderly Gilbert woman died in June.
As of Thursday, the county has confirmed 22 human cases of the disease. It is passed from infected bird to mosquito to humans.
"The folks who are getting reported are the ones who are the most sick. It's really, really the tip of the iceberg in terms of the number of people infected," said Dr. Bob England, director of the Maricopa County Department of Public Health. "Most people with West Nile will not have symptoms at all. About one in five will feel like they have the flu."
England said the number of people who have actually been infected with the virus - but have not suffered the severe symptoms - may be in the hundreds.
Last year, there were 20 reported human cases of West Nile in Arizona, all but one in Maricopa County. There were no reported deaths.
The virus can cause illness in people and horses. About 20 percent of those infected will develop symptoms such as fever, headache, body aches and muscle weakness between three and 15 days after a mosquito bite.
The more severe cases, which often strike the elderly, may include symptoms such as high fever, severe headache and neck stiffness. West Nile virus can cause encephalitis or inflammation of the brain as well as meningitis.
Arizona is leading the country this year in the number of human West Nile virus cases, according to the Centers for Disease Control and Prevention. The report lists only those cases which are severe, including those where victims suffer from neuroinvasive disorders such as meningitis or encephalitis.
Officials with the county health and environmental services department confirmed the East Valley is getting the brunt of the disease this year. The county has collected 110 West Nile virus-positive mosquito samples in traps, mostly in the East Valley, though reports are ramping up from all over the county. Last year, there were 51 West Nile virus-positive mosquito samples reported in the county.
"It has been unusually focused on the East Valley this season," England said. "We always say it's going to be all over the Valley because it is. But it is focused on the East Valley thus far."
England said his department is still investigating a number of possible human cases.
"If people are getting bit by mosquitoes, they need to decrease the habitat to circumvent that," he said, noting the need for residents to remove standing water from around their homes where mosquitoes can breed.
Part of the problem in the Valley is people who move here from other parts of the country don't believe mosquitoes are a problem because of what they're used too in higher humidity areas. They may overwater their grass or potted plants, which leads to standing water.
"What we do have are plenty of breeding of the type of mosquito that brews West Nile virus," the culex mosquito, England said.
Plus, with so many home foreclosures in the area, "green" swimming pools - those uncared for - are rampant. Because they are large bodies of standing water, the pools are the perfect breeding ground for mosquitoes.
The increased monsoon storms this week will likely mean even more mosquito activity, said Johnny Dilone, spokesman for the county's environmental services department. Parts of the East Valley were hit with heavy rain Wednesday night.
"We still have a couple more months to go for West Nile activity. With the monsoon and more storms and water, most likely we'll have stagnant water," he said.
The department conducts mosquito fogging in areas where there are either a great number of mosquitoes of any type caught in a trap or in areas where positive West Nile virus mosquitoes have been found. The county also works with municipalities if there are concerns. Dilone pointed to Tempe Town Lake where a dam burst earlier this month, causing the lake to drain and leaving puddles of stagnant water.
He said Tempe also had a vendor in place treating the area regularly for bugs and that company and the county would monitor for mosquito issues.
"That was one of the biggest concerns from the beginning. We've been in touch with the city and the assistant manager and the vendor," he said. "After this incident they right away came in to treat and assess the situation."
The county also works with other municipalities in identifying other public areas of concern.
"We don't just spray and leave. We'll be monitoring the area and make sure there are no mosquitoes in the area," he said. If there is a green pool or poorly maintained water feature or pond that is a breeding site, the county attempts to contact the person responsible to help prevent mosquitoes from breeding there again.
Residents can report trouble sites such as green pools anonymously.
Information about spraying can be found online at www.maricopa.gov/wnv or by calling (602) 506-0700.
To minimize the risk of mosquito-borne illness:
• Eliminate standing water, which allows mosquitoes to breed. Check for items outside the home that collect water, such as cans, bottles, jars, buckets, old tires, drums and other containers.
• Change water in flower vases, bird baths, planters and animal watering pans at least twice a week.
• Repair leaky pipes and outside faucets, and move air conditioner drain hoses frequently.
• Avoid bites when going outside at night in areas where mosquitoes are present by using insect repellent.
• Wear light-weight clothing that covers the arms and legs.
Source: Maricopa County Environmental Health Department