First Colorado Cases of West Nile Virus Confirmed
June 27, 2008 - DENVER - State health officials
have confirmed the first two human cases of West Nile virus
for the 2008 season. The cases were reported from Boulder
and Logan counties. Both patients are recovering from their
illnesses.
John Pape, an epidemiologist who specializes in
animal-related diseases
at the Colorado Department of Public Health and Environment,
explained,
“West Nile virus season is here. Now is the time to take
precautions
against West Nile virus, which is a preventable disease.
“West Nile virus can be avoided by eliminating mosquito
breeding
grounds in back yards, wearing insect repellent and using
other methods
to avoid mosquito bites when outdoors.”
The cooperative surveillance conducted by state and local
health departments started on June 1 has shown Culex
mosquito populations are still low but increasing.
Historically, populations of Culex mosquitoes, which
transmit West Nile virus, start to rapidly increase this
time of year as temperatures begin to rise. “Typically
around the first week of July we start detecting our first
positive mosquitoes, which the human cases show, already are
out there,” Pape said.
He said each season this virus will be present and
circulating around the state. The severity of the season
will depend on the weather.
“Within the next couple weeks we will have an idea of how
severe or mild this season may be,” he said.
Pape said 2007 was the second most active season for West
Nile virus cases following the 2003 epidemic. Last year,
Colorado reported 576 cases with 7 deaths. Ninety-nine
cases, or 17 percent, had meningitis or encephalitis,
indicating the virus had entered the central nervous system.
“However, we know that even West Nile fever, the less severe
form, can cause significant illness, last for weeks to
months and can result in people being hospitalized.
Prevention is the key,” Pape emphasized.
In reviewing statewide surveillance data from 2003 to 2006,
Pape said patterns of human infections have emerged.
“Approximately 85 percent of people who became ill with West
Nile virus were infected when bitten by an infected mosquito
during a six-week period from July 1 through the second week
of August. Therefore, we are entering the peak season of
West Nile virus transmission,” explained Pape.
Infected mosquitoes continue to feed through September and
early October, depending on the weather, but fewer than 10
percent of human cases are contracted after Labor Day, Pape
explained. “July and August are the highest-risk months of
being infected, and people should be extra diligent during
this time and use whatever methods available to avoid
mosquito bites. This is particularly important one hour
before sunset through around midnight, when Culex mosquitoes
are most actively feeding,” he said.
Pape said that individuals can reduce the number of
mosquitoes by cleaning out gutters and other places around
their homes where there are pools of standing water that are
good breeding places for mosquitoes. Such breeding grounds
include empty flowerpots, plastic swimming pools or old
tires.
“If you have a birdbath, remember to change the water at
least weekly. This also is a good time to repair torn window
and door screens,” he said.
Additional precautions to take against West Nile virus
include the following:
Use precautions or avoid outdoor activities, such as
gardening at dawn and after dusk when mosquitoes are most
active.
- If outside at dawn or after dusk, cover up by
wearing light, loose-fitting pants and long-sleeved
shirts, shoes and socks.
- Use approved mosquito repellents containing DEET,
picaridin or oil of lemon eucalyptus. DEET products
generally provide the longest protection. The other
repellents work but must be applied more frequently.
Follow the product label for correct use. Products with
10
percent or less DEET are recommended for children.
Colorado has experienced five full seasons of West Nile
virus transmission, each with different levels of
transmission. In 2006, there were 345 cases reported with
seven deaths. The mildest year thus far was 2005, when
Colorado had 106 human cases and two deaths. In 2004, cases
were moderate with a total of 291 human cases, including
four deaths. This represented a sharp downturn from the
first full season of West Nile virus in Colorado in 2003
when there were 2,947 confirmed human cases of the disease
and 63 deaths. Only 14 cases were reported in 2002, when the
virus was first detected in the state in August of that
year. Overall, Colorado has recorded 4,280 human cases and
83 deaths, although the total number of identified cases
represents only a small proportion of persons who actually
became ill during this time.
Pape advised anyone who finds a dead bird to call the
Colorado Health Emergency Line for the Public (CoHELP) at
1-877-462-2911. Mosquitoes
feed on infected birds and then pass on the virus to humans.
In addition to taking reports of dead birds, staff can
answer most questions about West Nile virus. The Rocky
Mountain Poison and Drug Control Center operates the hotline
under contract with the Department of Public Health and
Environment.
Prevention tips and additional information about West Nile
virus is available online at
www.FightTheBiteColorado.com .
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