A man has died from mosquito-borne St. Louis encephalitis, a somber start to the Valley’s mosquito season. The man, in his 40s, had other health problems that likely contributed to his death from the virus May 14, county health officials said Monday.
Mosquitoes trapped near his Tempe home have been sent to the Arizona State Laboratory for testing, though hospital lab results confirmed the cause of death.
Maricopa County health officials are fielding hundreds of complaints and spraying thousands of acres with insecticide, including areas near Tempe Town Lake and floodirrigation properties in Queen Creek where high concentrations of the blood-sucking insects have been reported.
No other signs of diseasecarrying mosquitoes have been detected yet this year in Arizona, but it’s only a matter of time. Mosquito traps, chicken flocks and dead birds have so far been negative for both St. Louis and West Nile viruses.
“Mother Nature’s calling the shots here, not us,” said Craig Levy, manager of the state Department of Health Services’ vector-borne/ zoonotic disease section. “On occasion, you have something just kind of come out of nowhere.”
Unlike West Nile, which made its much-heralded state debut in August 2003 and has since killed 21 people in Arizona, the St. Louis version has been around since 1964. Just 40 cases have been confirmed in Arizona, including three deaths since 1985.
Though far more unusual here, the St. Louis virus tends to be more serious than West Nile, with most cases resulting in full-blown encephalitis, or swelling of the brain, compared to about half of the 515 confirmed West Nile cases.
“Many years we don’t have any cases” of St. Louis encephalitis, said state epidemiologist David Engelthaler. “But when we do see it, it is usually a very significant illness.”
There is no vaccine and no cure for the mosquito-borne diseases. Prevention is key, and health officials worry that Arizonans have let down their guard because West Nile appears to be on the wane after peaking in 2004 with 391 cases and 16 deaths.
“West Nile virus has sort of become old news,” Levy said. “It’s that time of year when people need to start paying attention and protecting themselves. People should not assume that they are immune, because the odds are very, very high that they are not.”
The pace is expected to pick up with the first summer rains.
“Everything that’s been fogged this year is because we’ve caught too many mosquitoes,” said John Townsend, manager of the county’s vector control program.
County health workers routinely test for the diseases in mosquitoes, horses, dead birds and chicken flocks, including hens in Mesa and Laveen.
Once the virus is detected, the surrounding area is sprayed to kill adult mosquitoes, and larvicide is used in standing water to kill the eggs.
In the case of the man who died, mosquitoes were trapped near his Phoenix workplace and outside his Tempe home, but no obvious breeding grounds were found.
“Every now and then something comes right out of the blue,” Levy said. “Ninety percent of the time you can find it before it finds the people.”
The best breeding ground for mosquitoes includes homes and backyards, so health officials urge residents to eliminate standing water. Even a tiny amount of liquid — what’s left in the bottom of a soda can — is enough to breed mosquitoes.
The encephalitis viruses are spread through mosquitoes that feed on infected birds. But most people bitten by infected mosquitoes won’t develop any symptoms.
With West Nile, about 20 percent of people will develop flulike symptoms and fewer than 1 percent of the people who are infected develop encephalitis.
Those considered most at risk are the elderly, young children and those with compromised immune systems. Most of the victims of the West Nile virus have been individuals over 50.
Symptoms can include fever, cough, sore throat and general malaise, followed in severe cases by headache, nausea, vomiting, confusion, tremors and convulsions. Encephalitis can produce long-term neurological damage, including memory loss, paralysis and deterioration of fine motor skills.
IN YOUR YARD:
• Don’t allow water to stand for more than two days.
• Check for standing water in bird baths, pet dishes, buckets, cans, cups, outside toys, wheelbarrows, old tires, boats and flowerpots.
• Remove any water that collects on pool covers.
• Clear leaves and twigs from eaves, troughs and gutters.
• Fill in low areas in lawns.
• Repair leaky pipes and outside faucets.
• Let your neighbors know about potential mosquito breeding grounds on their property.
TO REDUCE THE CHANCES OF GETTING BITTEN:
• Stay indoors from dusk to dawn, when mosquitoes are most active.
• Wear loose-fitting clothing, long sleeves and long pants.
• Apply insect repellent containing DEET to clothing as well as exposed skin.
• Do not use insect repellent on children under 2.