Last year’s outbreak of West Nile virus was the largest yet, but fewer people died or had serious brain damage from it compared to 2002, federal officials said Friday.
The 9,006 cases of the mosquito-borne virus last year were more than double the 4,156 cases in 2002, although officials at the Centers for Disease Control and Prevention said the larger number of cases may reflect more testing.
CDC officials still consider 2002 to be the worst year for the United States because of 284 deaths and 2,944 cases of severe brain damage. Last year, 220 people died and 2,695 suffered severe neurological disease, the CDC said.
The agency has already begun preparations for this year’s season and is sending money to state health departments to help track the virus and educate people on how to avoid getting infected.
“We are fully prepared to have another large outbreak,” said Dr. Lyle Petersen, acting director of the CDC’s division of vector-borne diseases. “We can’t predict what will happen, so we need to be prepared.”
The virus is spread to people from mosquitoes that have fed on infected birds, the virus’ main host.
West Nile first appeared in the Western Hemisphere when it showed up in New York in 1999. Since then, it has spread across the United States, with Oregon and Washington the only continental states free of West Nile virus.
The 2003 outbreak revealed holes in health preparations. Even in hard-hit areas, people still were reluctant to take protective measures — such as wearing long-sleeved clothing or using bug spray.
Officials still don’t know why the disease erupts in some areas yet leaves others unscathed. Chicago had large outbreaks in 2002 yet hardly any last year. Areas such as New England, where West Nile has appeared for five years, suddenly had more cases last year than ever, Petersen said.
Rural America was hard-hit last year. “I think it’s going to be quite a challenge to try and figure out how to do prevention in rural areas,” Petersen said. “People are spread out.”