Cases of West Nile virus spiked in Georgia last year, likely fueled by drought conditions that allow the mosquito that spreads the disease to thrive. Health experts are expecting a similar number of cases this summer.

The disease remains rare in Georgia. But when it strikes, it can cause devastating paralysis, weeks-long fever, fatigue and other symptoms. It sickened at least 52 Georgians in 2007, up from eight reported cases in 2006, according to reports filed with the Georgia Division of Public Health.

Jim Gathany / CDC (ENLARGE)

While Georgia is home to 63 species of mosquitos, the Southern House Mosquito is the main type that spreads West Nile Virus in this part of the country. Unlike other species, this mosquito can thrive during a drought because it likes to breed in storm drains, which usually have at least a little water in them.

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Reports of the most serious form of the disease, which involves encephalitis and meningitis, also were up significantly. Last year, 25 of the state's reported cases involved serious neurological symptoms, compared with just two in 2006. The Centers for Disease Control and Prevention considers these cases the best indicator of disease activity because reporting is believed to be more complete than for less severe cases of West Nile fever, which often go unreported.

State health officials said they believe Georgia's drought is fueling the increase, though the exact cause is unknown.

The drought has reduced the number of nuisance mosquitoes in the state, health officials said. But the Southern House Mosquito, which spreads West Nile virus, likes to breed in small pools of water and storm drains — and its populations flourish when rain doesn't flush them away.

Unlike other hard-chomping mosquitoes, the Southern House Mosquito is "a little stealth biter and people just don't notice it," said Rosmarie Kelly, the division's public health entomologist.

Kelly suspects people slack off on applying insect repellent when they don't feel they're being swarmed or bitten, possibly also contributing to the sharp rise in West Nile cases. "It's likely to be an equally bad year as it was last year," she said. No cases have yet been reported in Georgia this year.

Elmer Gray, a public health extension specialist with the University of Georgia, agreed. "If it continues to be dry like it is now, there's reason to be concerned."

Local health departments often treat storm drains with a larvicide. But John Gormley, Fulton County's environmental health services director, said it's up to every resident to do their part. "If you've got mosquitoes, there's a good chance you're breeding them on your property," he said. "Once they hatch, they just don't fly that far."

Big culprits: buckets and other places water collects, including gutters. "If they're not properly cleared and sloped to the downspout, mosquitoes breed in those like crazy," Gormley said.

West Nile virus has only been identified in the United States since 1999. It was first detected in Georgia in 2001. It has since swept across the country, sickening people mostly in western and northern Plains states where another species of mosquito, Culex tarsalis, is particularly good at spreading the disease from infected birds to humans. The virus was first detected in Africa in 1937.

In 2007 nationally, there were 3,630 cases of West Nile virus disease, 1,217 of them involving serious neurological symptoms.

Nationally, the number of people developing severe neurological symptoms has been relatively stable in recent years. "It's kind of unexpected because in many parts of the Old World, where the virus has been endemic for years and years, you see a big outbreak and nothing for a number of years," said Dr. Lyle Petersen, director of the CDC's Division of Vector Borne Infectious Diseases.

It's unclear why the virus has developed this pattern in the United States, he said, but it may involve the particular strain of the virus that circulates in this country. It's more virulent, he said, more easily infecting birds and resulting in more human infections from mosquitoes that feed on both. Petersen, who is based at CDC's branch in Fort Collins, Colo., caught West Nile fever in 2003. "You just feel terrible for weeks and months on end. It will definitely ruin your summer."