West Nile Virus Has Caused Illness This Year in 27 States

ATLANTA, Aug. 20 -- West Nile virus cases this year are running a little ahead of last year, according to the CDC.

As of Aug. 14, 27 states have reported a total of 444 cases of human West Nile Virus illness, with California topping the list with 86 cases and five deaths, the CDC reported in the Aug. 17 issue of Morbidity and Mortality Weekly Report. In all, there have been 15 fatal cases this year,

The MMWR report noted that 54% of the infections occurred in men. The median age of the patients was 48 (range: two to 96), while the dates of illness onset ranged from March 25 to Aug. 5.

After California's 86 cases, Colorado followed with 72, and then the Dakotas, Arizona, Idaho, Minnesota, Mississippi, Nebraska, and Wyoming, each reported more than 10 cases.

The number of cases reported by states individually were: Alabama (seven), Arizona (16), Arkansas (three ), California (86), Colorado (72), Connecticut (two), Georgia (three), Idaho (13), Illinois (eight), Iowa (two), Kansas (five), Minnesota (15), Mississippi (14) Missouri (four), Montana (six), Nebraska (16), Nevada (two), New Mexico (eight), North Dakota (52), Ohio (one), Oklahoma (2), Pennsylvania (one), South Dakota (62), Texas (seven), Utah (two), Virginia (one), and Wyoming (34).

In addition to the five deaths in California, there were two in South Dakota. There was one death in Alabama, Arkansas, Colorado, Illinois, Mississippi, North Dakota, Oklahoma, and Wyoming.

Among states with no reported cases this year were Maine, New Hampshire, Vermont, Rhode Island, Maryland, West Virginia, Kentucky, Washington, Alaska, and also the District of Columbia.

The CDC also said that 49 presumptive West Nile viremic blood donors were reported through ArboNET during 2007.

Of these, 19 came from California; seven from Texas; five each from Colorado and North Dakota; three each from Kentucky and South Dakota; two from Minnesota; and one each from Arizona, Iowa, New Mexico, North Carolina, and South Carolina.

Of these 49 presumptive West Nile viremic blood donors, 15 (median age 49, range 18 to 79) subsequently developed West Nile fever.

So many factors influence outbreaks -- weather, birds, protection, environmental changes -- that activity throughout the years has not been not consistent, a CDC spokesperson said.

For example in 2002, California had only one case and in 2003, three cases. Compared with the current 86 cases, California had 278 in 2006, while Texas, now with only seven, had 354. Vermont and New Hampshire with no cases so far this year each had three in 2003.

Other findings:

• 539 dead corvids (members of the crow family) and 165 other dead birds with West Nile infection were reported in 24 states thus far this year.
• Infections have also been reported in horses in 17 states, in seven squirrels in California, and in two unidentified animal species in Idaho and Montana.
• West Nile virus seroconversions were reported in 189 sentinel chicken flocks in six states (Arizona, California, Florida, Iowa, North Dakota, and Utah) and Puerto Rico.
• A total of 1,845 West Nile-positive mosquito pools have been reported from 31 states.

The CDC advised those who garden or spend a lot of time outdoors there to use insect repellents, eliminate standing water pools that are mosquito breeding sites, install house screens, and join community projects for mosquito control.

The CDC recommended repellants containing DEET (N,N-diethyl-m-toluamide), or Picaridin (KBR 3023).

Eucalyptus [active ingredient: p-menthane 3,8-diol (PMD)], a plant- based repellent, is also registered with the EPA, the CDC investigators said. In two recent scientific publications, when oil of lemon eucalyptus was tested against U.S. mosquitoes, it provided protection similar to repellents with low concentrations of DEET.