West Nile virus cases rising; 40% increase in one week: 66 dead in U.S.

August 29, 2012 – HEALTH – One of the worst outbreaks of West Nile virus to ever hit the United States continues to expand, with 66 deaths and 1,590 illnesses reported as of Tuesday, according to the U.S. Centers for Disease Control and Prevention. Cases have jumped 40 percent nationwide since just last week, the agency added. Cases have now reached their highest level since the mosquito-borne virus was first found in the United States in 1999, agency officials said in a Wednesday press briefing. While almost all states have reported at least one case of West Nile illness, over 70 percent of cases have come from six states — Texas, South Dakota, Mississippi, Oklahoma, Louisiana, and Michigan. The outbreak has hit hardest in Texas, where nearly half (45 percent) of the total U.S. cases have been reported. “The number of people reported with West Nile virus continues to rise,” said Dr. Lyle Petersen, director of the CDC’s Division of Vector-Borne Infectious Diseases. “We have seen this trend in previous West Nile epidemics, so the increase is not unexpected,” he added. “In fact, we think the reported numbers will get higher through October.” According to Peterson, of the cases reported so far, 56 percent are what is called neuroinvasive disease, when the virus enters the nervous system causing conditions such as meningitis or encephalitis. The remaining reported cases (44 percent) are non-neuroinvasive. “These numbers represent a 40 percent increase of last week’s report of 1,118 total cases and 41 deaths,” Petersen said. These numbers can be somewhat misleading since most cases of West Nile are non-neuroinvasive and are mostly unreported, the CDC said. That means that the number of unreported cases probably far exceeds reported ones. Neuroinvasive disease is the most serious for of West Nile infection and these patients usually are hospitalized, Petersen said. The size of the outbreak is based on these cases since they are the ones easily identifiable, he added. The only states that have not reported cases are Alaska and Hawaii, he said. “Based on current reports, we think the number of cases may come close to, or even exceed, the total number reported in the epidemic years of 2002 and 2003, when more than 3,000 cases of neuroinvasive disease and more than 260 deaths were reported each year,” Petersen said. The reasons for a major outbreak this year aren’t clear, Petersen said. The drought in Texas may have played a role, but there were probably other factors as well, he added. The best way to avoid the virus is to wear insect repellant and support local programs to eradicate mosquitoes, Petersen said. There are currently no treatment for West Nile virus and no vaccine to prevent it, he added. Speaking at the press conference, Dr. David L. Lakey, Commissioner of the Texas Department of State Health Services said that, “As I look at the data, I am not convinced that we have peaked. Since last week, there have been 197 new cases and 10 more deaths in Texas, Lakey said. “Those numbers will continue to go up,” he added. –US News

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