Jun 1, 2004 (CIDRAP News) The nation's first human cases of West Nile virus (WNV) infection were reported last week in New Mexico and Arizona, marking the first time the West Nile season has begun so far west.
The New Mexico Department of Health announced last week that a man in San Juan County had tested positive for the virus and had recovered after having only mild symptoms.
In Arizona, Maricopa County health officials in Phoenix said last week that a local man became ill May 8 with what turned out to be WNV infection. He subsequently recovered.
The Ohio Department of Health reported a probable WNV case in a 79-year-old man Apr 9, but the Centers for Disease Control and Prevention (CDC) eventually concluded that he had acquired the virus last year, according to CDC spokesman Llelwyn Grant in Atlanta. "It was believed that the virus was present from the previous season," he told CIDRAP News.
The debut of West Nile this year was slightly later than in the past 2 years but earlier than in 2000 and 2001, according to Grant. Last year the first confirmed human case was reported Apr 14 in Texas, and in 2002 the first case showed up May 19 in Washington, DC, he said. The first case of 2001 was logged July 13 in Florida, and in 2000 the first case was identified July 20 in New York City.
WNV has moved steadily westward since it first emerged in the New York City area in August 1999. Last year was the first year the virus was found west of the Continental Divide. Birds are the natural host for the virus, which is spread by mosquitoes.
The only states that have yet to see their first known human cases of the infection are Washington, Oregon, Alaska, and Hawaii, Grant said. California had three cases last year.
The nation had a total of 9,862 human cases in 2003, with 264 deaths, according to the CDC. The Great Plains were hard hit; Colorado alone had 2,947 cases.
CDC information on current WNV activity
CDC's 2003 WNV case statistics