Reuters
6:37 p.m. EST, September 5, 2012
(Adds details, comment from Texas health official)
By Marice Richter
DALLAS, Sept 5 (Reuters) - The number of U.S. cases of West
Nile virus rose 25 percent in the latest week, putting the 2012
outbreak of the mosquito-borne disease on track to be the most
severe on record in the United States, health officials said on
Wednesday.
It's already the worst year ever in Texas, they said.
So far this year, 1,993 cases have been reported to federal
health officials, up from 1,590 reported the week before, the
Centers for Disease Control and Prevention said in its weekly
update of outbreak data. A total of 87 people have now died from
the disease, compared with 66 reported one week ago.
The disease has been reported in people, birds or mosquitoes
in 48 U.S. states, so far absent only in Alaska and Hawaii.
About half of all human cases are in Texas, the CDC said.
Of the nearly 2,000 cases reported to the CDC this year,
1,069, or 54 percent, are of the severe neuroinvasive form of
the disease, which can lead to meningitis and encephalitis.
The milder form of the disease causes flu-like symptoms and
is rarely lethal.
Texas, the outbreak's epicenter, has had 40 deaths and 495
neuroinvasive cases this year, said Dr. David Lakey,
commissioner of the Texas Department of State Health Services.
About a quarter of the cases have been in Dallas County, he
said. "This is our worst year ever in Texas," Lakey said.
The previous Texas record was in 2003, when there were 40
deaths and 439 neuroinvasive cases.
Texas has had 1,013 cases overall this year, Lakey said.
CDC figures - which sometimes lag behind state data - show
that South Dakota has the next-highest number, with 119 cases
and two deaths.
More than 70 percent of the cases have been reported from
Texas, South Dakota and four other states: Mississippi,
Oklahoma, Louisiana, and Michigan, the CDC said.
The CDC said the number of cases so far this year is the
highest reported to federal health officials through the first
week in September since the disease was first detected in the
New York City in 1999. The worst outbreak overall occurred in
2003, with 9,862 cases and 264 deaths for the full year.
The disease is thought to have originated in Africa.
This year's outbreak is already nearly three times the size
of last year's, when 712 cases were reported nationally, with 43
deaths.
In Texas, aerial spraying during the last several weeks in
Dallas County and neighboring Denton County have been effective
in reducing the mosquito population that transmits the virus
from infected birds to humans and other mammals, Lakey said.
West Nile outbreaks tend to be unpredictable. Hot
temperatures, rainfall amounts and ecological factors such as
the bird and mosquito populations have to align just right to
trigger an outbreak like the one this year.
Drought can reduce mosquito population while heavy rains can
wash out breeding sites, said Dr. Lyle Petersen, director of the
Division of Vector-Borne Infectious Diseases for the CDC.
Cities are more prone to outbreaks even during a drought
because of widespread use of sprinkler systems and standing
birdbaths that can cause water to pool and become breeding
grounds for mosquitoes.
"We've seen cases in places like Phoenix, which is in the
middle of the desert" because of standing water, Petersen said.
(Additional reporting by Dan Burns; editing by Corrie MacLaggan
and Todd Eastham)
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