five-year study of survivors suggests.
One in 150 people infected with West Nile virus get severe neurological
disease. More than 40% of these patients may have serious symptoms for the
rest of their lives, say Kristy Murray, PhD, DVM, University of Texas Health
Science Center at Houston, and colleagues.
The finding comes from five years of data on 108 Houston-area residents who
came down with severe West Nile disease after infection with the mosquito-borne
virus. Murray's team evaluated the patients every six months.
A year after their West Nile virus infection, 60% of these patients still
had serious symptoms. Five years later, 42% had not fully recovered -- and
weren't getting any better.
These lasting symptoms included fatigue, muscle weakness, depression,
difficulty walking, memory loss, and personality change.
"For patients with severe West Nile disease, long-term neurological
complications are significant and should be expected," Murray tells WebMD.
"At around the two-year mark, the recovery that is going to happen has
happened. Those with symptoms continue to report them. Some say they get worse
at times, not better."
This doesn't happen to the vast majority of people who get bitten by a
mosquito carrying West Nile virus.
"Eighty percent of people infected with West Nile virus have no symptoms
-- they don't even know they are infected," Murray says. "Most of the
other 20% have a mild, flu-like illness with no worries in terms of recovery.
But here we see the tip of the West Nile iceberg: those with more severe
People over age 50 are more likely than younger people to get severe West
Nile disease. But while the average patient in her study was 52 years old,
Murray saw severe disease in children, too. One was only 6 months old; another
was 11 years old.
Severe West Nile disease includes
high fever leading to hospitalization,
encephalitis , and polio-like paralysis. West Nile meningitis affects the
protective membranes covering the brain and spinal cord. West Nile encephalitis
is a more serious infection of the brain. Murray and colleagues found that 60%
of patients with West Nile encephalitis still have symptoms after five
One of the study's most disturbing findings is that 31% of people with
serious West Nile disease reported clinical depression. Also disturbing is that
25% of patients reported personality changes. They became more irritable and
"Their families said they had a short fuse, easily lost their tempers,
and had decreased socialization," Murray said.
Patients also often had balance problems that made it difficult for them to
walk normally. Other nervous system symptoms included loss of strength, sensory
loss, hearing loss, posture problems, and tremors.
"People really need to protect themselves against mosquito bites. You
never know where on the scale of West Nile infection severity you are going to
fall," Murray says. "Just because people are younger does not mean they
can't be severely affected. And if they are older, they definitely need to be
more careful in terms of exposure."
Murray announced the findings in a report to the 2008 International
Conference on Emerging Infectious Diseases, held March 6-19 in Atlanta.
By Daniel DeNoon
Reviewed by Louise Chang
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