West Nile cases stay ahead of 2006 pace

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Aug 17, 2007 (CIDRAP News) – The count of West Nile virus (WNV) cases in the United States so far this year remains ahead of last year's pace, but fewer severe cases have been reported, according to the latest numbers from the Centers for Disease Control and Prevention (CDC).

As of Aug 14, 444 WNV cases, including 15 deaths, had been reported from 27 states, the CDC says in today's issue of Morbidity and Mortality Weekly Report. That compares with 388 cases and 13 deaths in 26 states at this time last year, as reported in the Aug 18, 2006, MMWR.

Neuroinvasive cases—the severe form of the disease, including West Nile meningitis, encephalitis, and myelitis—make up 30.6% (136 of 444) of cases so far this year, as compared with 40.7% (158 of 388) at this time last year, according to CDC figures. (Nine cases this year were unclassified, as were 13 at this time last year.)

California has been hit hardest this year, with 86 cases, including 32 neuroinvasive illnesses. Colorado is second with 72 cases (10 neuroinvasive), followed by South Dakota, 62 (19), North Dakota, 52 (8), and Wyoming, 34 (5).

Screening of donated blood has led to the identification of 49 donors with presumed WNV infection so far this year, the CDC reported. Fifteen of the donors subsequently had West Nile fever. Nineteen of the 49 donors were from California.

West Nile cases in the United States jumped sharply last year, totaling 4,269, a 42% increase over the 3,000 cases recorded in 2005, according to the CDC. Neuroinvasive cases were 34% of the total in 2006 and 43% of the total in 2005. The record year for reported cases was 2003, with 9,862.

See also:

CDC. West Nile virus update—United States, January 1-August 14, 2007. MMWR 2007 Aug 17;56(32):821-2 [Full text]

Jul 26 CIDRAP News story "Number of West Nile virus cases surges"

WNV report in Aug 18, 2006, MMWR
http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5532a3.htm

CDC West Nile page
http://www.cdc.gov/ncidod/dvbid/westnile/index.htm

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