West Nile Fever Worse Than Expected

Sept. 6, 2004 -- West Nile fever is more severe and lasts longer than experts initially thought, new research shows.

Spread through the mosquito-born West Nile virus, symptoms include fever, nausea, vomiting, headache, muscle pain, and skin rash.

However, West Nile fever stops short of the virus' scariest results -- infections of the brain (encephalitis) or its coverings (meningitis).

Not much is known about how West Nile fever plays out. Until now, it was thought to be fairly mild, lasting three to six days.

That's not what John Watson, MD, MSc, of Chicago's Public Health Department found when he and colleagues talked to veterans of West Nile fever.

Watson's team interviewed 98 people who had contracted West Nile fever, according to the Illinois Department of Health. They had no signs of paralysis or any indication that the infection spread and had caused encephalitis or meningitis.

Speaking to participants a few months after the illness, the researchers asked the participants about 18 different symptoms, hospitalization or other medical attention, and impact on daily activities.

What they heard defied conventional wisdom about West Nile fever.

Worse Than Expected

On average, it took patients 60 days to get back to normal, not the handful of days previously assumed. Almost all said they had felt fatigued, and half were tired for 30 days or longer.

Nearly one-third were hospitalized for at least a day; the longest hospitalization was 56 days.

Age didn't matter; older and younger patients took about the same time to recover.

West Nile fever also limited their activities: 57 missed school or work -- on average 10 days were lost although this ranged from one day to greater than three months. Forty-seven people with West Nile fever had difficulty walking, 89 reduced their out-of-home chores, such as shopping and yard work, and 69 cut back on exercise.

More than half the group reported fever, headache, muscle pain/weakness, neck pain, and concentration problems. Of those reporting muscle weakness, 83% said that symptom lasted more than seven days.

"West Nile fever is a more severe illness than has previously been documented," write the researchers in the journal Annals of Internal Medicine.

Rare Cases

These people were the exceptions; most people don't get sick after being bitten by a mosquito carrying the West Nile virus.

Only about 20% of people infected with the West Nile virus develop any symptoms. In fact, the majority don't know they've been infected unless their blood is screened.

Prevention Tips

Relatively few mosquitoes carry the West Nile virus, but since no one wants to be among the few who get infected, here are some ways to limit your exposure:

• When going outdoors into mosquito-borne areas, use insect repellents containing DEET (N, N-diethyl-meta-toluamide).
• Consider staying indoors during dawn and dusk, when mosquitoes are most active. If you do go out, wear long sleeves and pants. Light-colored clothing is best for spotting mosquitoes that land on you.
• Put screens on your windows and doors.
• Empty standing water from flowerpots, buckets, and barrels, which are all popular places for mosquitoes to breed.
• Change the water in pet dishes and replace the water in birdbaths weekly.
• Drill drainage holes in tire swings so water drains out.
• Keep children's wading pools empty and on their sides when not in use.