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West Nile Virus: Who's at Risk?

As Cases Climb, Experts Answer the West Nile Virus Questions Everyone Asks

What is a typical time frame from bite to symptoms?

From bite to symptoms can take three to 12 days, Staples says. "It's usually three to six."

Typically, first symptoms include fever, chills, feeling poorly, and lacking an appetite, Schaffner says.

At that point, especially if you live in a highly affected area, it is reasonable to call your doctor, he says.

It could well be something else, such as a urinary tract infection, he says.

If you are infected, what is the usual course?

"The people who develop the less severe illness report feeling sluggish for weeks or [sometimes] months," Staples says.

"For those who develop the more serious complications, about 10% will die."

Those who survive can have long-lasting neurological effects. One example is a condition called acute flaccid paralysis. The patient is unable to move arms or legs. That is rare, she says.

Long-lasting kidney effects may occur, says Schaffner. Preliminary research has found a gradual decline in kidney function in some patients.

"It is a slight decline, but it is progressive," he says. "There is no sense yet this will lead to kidney failure."

More research and follow-up is needed, he says.

There is no specific antiviral medicine for the infection, Schaffner says. Doctors instead treat the individual symptoms of each person.

What is the best way to avoid getting infected with West Nile virus?

After avoidance, experts advise using insect repellents with DEET, but not in infants less than 2 months old.  

Schaffner has some more suggestions:

  • Parents can avoid taking walks with infants early in the morning or at dusk.
  • Put mosquito netting over baby carriages and apply repellent to the carriage itself.
  • When outdoors, wear long pants and long sleeves.
  • Remove standing water from around your house, including in gutters, kiddie pools, and potted plant saucers.

What is in the aerial spray being used in some areas, and is it safe?

The exact insecticides used depend on the region, says William Reisen, PhD, director of the Center for Vectorborne Diseases at the University of California, Davis.

Most common, he says, are synthetic pyrethroids, derived from petroleum derivatives, or organophosphate compounds.

Synthetic pyrethroids are often found in garden insecticides.

"Everything they are applying is approved by the EPA," he says. The vehicles dropping it account for the wind and other factors, he says.

"All the health departments and mosquito departments involved always announce when they are spraying. They suggest people remain indoors and limit time outdoors while the spray is occurring."

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