PHOENIX -- Maricopa County Department of Public Health confirmed its first 2010 death from West Nile virus.
It was announced Wednesday that the victim, an elderly woman with pre-existing health conditions, was a resident living in the East Valley.
Ten people in Maricopa County have tested positive for West Nile virus so far this year. Most of the cases were in the East Valley.
"Unfortunately, most of these cases have the more severe form of West Nile virus, which is meningitis and/or encephalitis," said Craig Levy with the Arizona Department of Health Services.
"Because most people with milder symptoms of West Nile stay at home and don't seek medical care, we rarely hear of these cases," Levy continued. "That means there are a lot more people sick with West Nile than we know of."
West Nile virus is transmitted through the bite of an infected mosquito. So far this year, more than 100 mosquito samples have tested positive for West Nile virus all over the state, although many have been in the East Valley.
"Maricopa and Pinal counties have been finding a lot of positive mosquitoes in the East Valley, so it is not surprising the human cases are from that area," Levy said.
However, he warns that everyone in Arizona needs to be cautious.
"Just because the first mosquitoes and human cases were in that area, it is not limited," Levy said. People all over Arizona need to take this seriously."
West Nile virus can cause severe illness in people and horses, although only about 20 percent of those infected will develop flu-like symptoms, including fever, headache, body aches and muscle weakness.
Some people, especially the elderly, may experience more severe symptoms including high fever, severe headache, neck stiffness, and/or encephalitis or inflammation of the brain.
Health officials from Maricopa and Pinal counties, as well as ADHS, urge all people to "Fight the Bite" and follow simple precautions to avoid mosquitoes and the diseases they may carry:
• Avoid outside activity between dusk and dawn, when mosquitoes are most active.
• Wear lightweight clothing that covers your arms and legs and use an insect repellent if you must be outdoors when mosquitoes are active. Always follow the directions on the label.
• Make sure doors and windows have tight-fitting screens and remain closed.
• Eliminate mosquito-breeding sites around your home by removing standing water in potted plants, tires, bird baths and other containers where water may collect.
• Ensure that swimming pools and decorative water features are properly maintained.
• Change water in flowerpots, bird baths and pet bowls located outdoors at least twice per week.
Many local vector control programs around the state have been treating mosquito breeding habitats and some counties have been fogging to kill the specific mosquito that spreads West Nile virus. If you notice green pools in your neighborhood, talk to your neighbors or notify your county.
West Nile virus was first found in Arizona in 2003. Since then, more than 900 human cases have been reported. The worst year was 2004 with 391 human cases and 16 deaths. Last year, there were only 20 human cases of West Nile in Arizona and no deaths.