The nation is on pace to have its worst West Nile virus season in years, federal health officials said Thursday.

So far this year, there have been nearly four times as many cases reported as there were at the same time last year. However, cool weather in August or September _ when the bulk of West Nile cases usually occur _ could take the sting out of the season, officials added.

"If this trend continues like this, it's going to be a very high," said Dr. Lyle Petersen of the U.S. Centers for Disease Control and Prevention.

Nineteen states, most of them west of the Mississippi, have reported 122 human cases of the mosquito-borne disease. That total includes three deaths. Health officials had counted only 33 cases by late July last year but it turned out to be the worst season since the record year 2003.

At least 177 people died from West Nile in 2006 out of 4,269 cases; 264 people died out of nearly 10,000 cases in 2003.

West Nile virus was first reported in the United States in 1999 in New York, then spread across the country. Only about one in five infected people get sick. Severe symptoms including neck stiffness, disorientation,coma and paralysis.

A variety of signs say this could be a bad year. In Georgia, for example, a recent drought helped cause a more than threefold increase in the number of disease-transmitting mosquitoes.

There have not yet been any reported human cases in the state. "(But) if you just look at number of mosquitoes we're seeing, it should be a bad year," said Rosmarie Kelly, entomologist with the Georgia Division of Public Health.

A fast start isn't always a good predictor of how bad the year will be, Petersen noted. In 2003, only nine cases were reported at this point. In 2004, a relatively mild year, 182 cases were reported as of late July due mainly to an unusual early outbreak in Arizona, Petersen said.

Mosquitoes transmit the virus, often picking it up from birds they bite and then spreading it to people. A variety of factors influence the disease's impact, including heat waves, weather conditions and the species of mosquitoes and birds in a given area, Petersen said. West Nile season usually peaks in late August and doesn't end until November.

Health officials warn the public to use mosquito repellent, install and repair screens and eliminate standing water and other mosquito breeding areas.