The west nile virus first appeared in the United States in 1999. According to statistics, human cases popped up in 40 states plus the District of Columbia last year, killing hundreds, and making thousands more sick. And health officials expect to see the virus in 48 states this year.
By the end of 2002, the virus's march across America left almost 4,000 people infected and 254 dead. But the flu-like symptoms, which include fever, headache, and body aches, are common. So many people never know they are infected. In fact, officials estimate that for every one individual that becomes severely ill, there could be as many as 200 more that were infected and didn't know it. And for that reason, many believe the number of people in America who have had the disease is actually much higher than the statistics imply. They now estimate around 750,000 to 1,000,000 people were infected just last year. They say that's good news in a way, though, because once you're infected, you become immune to the disease. And when enough people are immune, West Nile Virus won't be such a big problem anymore.