The first person to contract the potentially deadly West Nile virus in Nevada this year is an 84-year-old Clark County man, according to the Southern Nevada Health District.
The unidentified man was diagnosed with the more serious neuroinvasive form of the illness, West Nile encephalitis, and was hospitalized. He is expected to recover.
The case comes a few weeks after infected mosquitoes were found in the Logandale area, about 50 miles northeast of Las Vegas.
But it's possible he contracted the disease in the Las Vegas Valley, which has experienced a spike in neglected swimming pools because of a significant increase in the number of abandoned homes in the foreclosure capital of the nation.
These pools have turned green and filled with algae, becoming perfect breeding grounds for mosquitoes that sometimes plant the virus into human beings.
West Nile season starts in late summer and ends in early fall. The virus is spread by mosquitoes that feed on infected birds and then bite humans.
The Southern Nevada Health District classifies the less dangerous form as West Nile fever, nonneuroinvasive, and the more serious form as West Nile Encephalitis, neuroinvasive.
In most cases -- with the less serious type -- people aren't even aware they are sick, health officials say. But if they do fall ill, the symptoms are no more serious than what one would experience with a common cold, such as fever, headache, nausea, diarrhea, loss of appetite and an achy back and muscles. Some might also develop a skin rash.
"Only about one in every 150 people infected with West Nile virus develop the serious form of the disease," health district spokeswoman Jennifer Sizemore said.
The severe cases affect nervous systems and can cause encephalitis, which is inflammation of the brain, and meningitis, which causes inflammation to the membrane around the brain and spinal cord.
Paralysis from inflammation to the spinal cord can cause a sudden onset of weakness in the limbs and breathing muscles, according to the U.S. Centers for Disease Control and Prevention in Atlanta. Some people lapse into a coma.
Those most at risk are the very young and very old who have underlying health issues.
There is no specific treatment for the virus other than hospitalization, where fluids are administered intravenously.
The virus first appeared in the United States in 1999 in New York City. Since then it has spread across the continent. Authorities think an infected bird was imported to the United States, from either Africa or Europe, where it is common.
GREEN POOL THREAT
Sizemore said officials have not determined where the Clark County man contracted the disease, or exactly where he lives, but it's likely he was bitten somewhere in the county.
But she said that the green pool danger might have been worse if it weren't for a public awareness campaign the health district launched a few years ago and efforts by the cities and the county to control the mosquito problem in these backyard breeding grounds.
"Our biggest message is this is preventable," Sizemore said. "Our aggressive action and pubic awareness has helped. People know to call when they see a problem, and they do."
With the exception of a bump at the end of the decade, the numbers bear her out:
Since 2004, the first year the virus was detected in Clark County, 23 cases were recorded; 13 of them were the more serious form and 10 of the less dangerous.
The number dropped to seven in 2005, three in 2006 and two in 2007.
A notable increase occurred in 2008 when a dozen cases were reported -- in proportion perhaps to foreclosures but still almost only about half the number reported in 2004.
In 2009, there were 10 cases, and last year there were none.
"As you can see, the first year was highest, and subsequent years have been much lower, even with the increases in 2008 and 2009," Sizemore said.
In Clark County, the health district no longer treats green pools on private property. That job has fallen to the city and county code enforcement agencies.
Las Vegas spokesman Jace Radke said the number of green swimming pools in the city has increased dramatically in recent years because of the high number of home foreclosures.
In 2009, Las Vegas code enforcement cited 276 owners of green swimming pools. In 2010, the number jumped to 544. And through the first seven months of 2011, there have been 448 citations, Radke said. The city pumped the water out of 602 of those 1,268 pools.
"It was quite a jump," he said.
A single green swimming pool can produce millions of potentially infected mosquitoes over the course of a summer, according to the California Department of Health and Human Services.
Thus far this year, 53 cases of West Nile virus have been reported nationwide, with Mississippi having the most cases at 14. Of those, 32 were the more serious type and two deaths have been reported: one in Mississippi and one in Texas.
The CDC points out there are likely far more nonneuroinvasive cases that simply go unreported because treatment is not sought.
Contact Review-Journal reporter Doug McMurdo at firstname.lastname@example.org or 702-224-5512.