|
|
|
|
||
|
||
|
|
||
| SEARCH | SUBSCRIBE | ||
|
 |
Reason
elderly are susceptible to West Nile unclear, expert says By Jim Erickson Rocky Mountain News, August
6, 2003 Conventional
wisdom tells us that the elderly are more likely to die from West Nile
virus because their immune systems are weak and they can't fight off the
infection. Not so, says Dr. Roy Campbell, a
medical epidemiologist at the Centers for Disease Control and Prevention
in Fort Collins. "It's an urban
legend," Campbell said Tuesday after health officials announced that
a 77-year-old Greeley woman became Colorado's first human West Nile virus
fatality. Family members said the woman
suffered numerous health problems that weakened her and made her
susceptible to West Nile. But most West Nile victims - including the
elderly ones - do not have impaired immune systems, Campbell said. "The reason age seems to be
a risk factor for severe illness with West Nile infections is
unknown," Campbell said. "There's nothing that you can
generalize about increasing age that explains why this happens." But it does happen. Last year, 284 Americans were
killed by West Nile. The average age of the victims was 77.5. They ranged
in age from 19 to 99, and 64 percent of them were male. Ninety-two percent of last
year's fatalities (261 of 284) involved West Nile encephalitis, an
inflammation of the brain that causes swelling, cell death and numerous
complications, said Campbell, who recently submitted a summary of the 2002
West Nile epidemic to the New England Journal of Medicine. Fifteen of last year's West Nile
victims died from meningitis, an inflammation of the membranes that
envelop the brain and spinal cord. Seven of the 284 deaths were
blamed on West Nile fever, a normally mild illness that can include fever,
headaches, body aches, a skin rash on the chest and swollen lymph nodes. One of the 284 deaths was
unclassified. Since West Nile fever sufferers
rarely die and often don't seek medical attention, West Nile fatality
rates are computed by counting the number of meningitis and encephalitis
patients who die. Last year, 9.4 percent of West
Nile encephalitis and meningitis patients died in the United States. That
figure is comparable to the death rate in recent West Nile epidemics in
Romania, Israel and Russia, Campbell said. Colorado's 72 West Nile cases
include 50 West Nile fever cases, 13 meningitis and nine encephalitis
cases. One death out of 22 severe
Colorado illnesses is a fatality rate of just 4.5 percent, but that number
is likely to rise as the summer wears on, Campbell said. "I can almost guarantee you
that, as the season goes along, somewhere around 10 percent of
encephalitis cases will be fatal," he said. It's impossible to predict how
many West Nile illnesses and deaths Colorado will record in 2003. Factors affecting the final
outcome include: the abundance of the virus in wild birds; the number of
mosquitoes and their species; the proximity of mosquitoes to human
populations; the West Nile infection rate among those mosquitoes; personal
protective action taken by Coloradans; mosquito-control efforts
implemented by cities; and weather. "All these things can
interplay into whether or not humans become infected and to what
extent," said Dan O'Leary, CDC's West Nile surveillance coordinator. "It's extremely complex,
and science has never been able to validly estimate how many cases will
occur in a given area in a given epidemic," O'Leary said. Last year, two-thirds of this
country's West Nile encephalitis and meningitis cases occurred during a
five-week period from mid-August to mid-September, said Dr. Tony Marfin, a
CDC medical epidemiologist. "The peak of the epidemic
is ahead of us," Marfin said. Copyright
© 2002 Global Action on Aging
|
