West Nile virus cases continued their steep rise around the nation this week, threatening to make this one of the worst outbreaks on record, federal officials say.
West Nile virus cases have reached 1,221 nationally, with 43 deaths, a substantial increase from last week, the Centers for Disease Control and Prevention reported Wednesday.
"The number of West Nile cases in people has risen dramatically in the last few weeks and indicates that we are in one of the biggest West Nile virus outbreaks we have ever seen in this country," said Lyle Petersen, director of the CDC's Division of Vector-borne Infectious Diseases.
This year, 47 states have reported West Nile virus in humans, birds or mosquitoes, the CDC indicated. Thirty-eight states have reported the human disease.
The 1,221 cases are the highest number of West Nile virus disease cases reported to the CDC through the third week in August since West Nile virus was first detected in the United States in 1999, the agency said.
Approximately 75% of the cases have been from five states: Texas, Mississippi, Louisiana, South Dakota and Oklahoma.
Texas has been hit hardest, with more than half of all cases in that state. As of Wednesday there had been 23 deaths and 640 cases there, said Christine Mann of the Texas Department of State Health Services.
Last Wednesday, there had been 693 cases nationally, with 26 deaths.
About 80% of people infected with the West Nile virus have no symptoms. Up to 20% of people who contract the virus develop symptoms that include fever, headache, body ache, swollen lymph glands and occasionally a rash on the trunk of the body. They appear within two to 15 days and then disappear within a few days.
Although it is a mild illness for some people, for others, "symptoms can last for many weeks or months," said the CDC's Petersen, who himself had it.
Of those who develop a fever, fewer than 1% develop West Nile neuroinvasive disease, which causes inflammation of the brain, spinal cord or the tissue surrounding the brain. "A fairly high proportion of those people who do survive have long-standing symptoms," either problems with thinking or paralysis, Petersen said. About 10% will die.
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