Although officials are expecting fewer West Nile virus cases in Evanston next year, some of this year’s victims could end up developing long-term neurological problems, including fatigue, memory loss, walking difficulties, muscle weakness and depression, according to local health officials.

These symptoms can result from encephalitis, a serious swelling of brain tissue that is the chief cause of death from West Nile. Evanston Health and Human Services reported symptoms of this or other neurological disorders in about 80 to 90 percent of the 40 local West Nile cases.

“We observed symptoms of muscle breakdown, tremors, photophobia and double vision,” said Evanston Communicable Disease Coordinator Mary Scott.

Dr. Mauro Dal Canto, a neuropathologist at Northwestern Memorial Hospital, said the West Nile encephalitis attacks the gray matter of the brain, kills neurons and renders the victim neurologically handicapped.

The effect of the West Nile encephalitis is similar to a stroke to the brain, he said.

Dr. Richard Munson, a neurologist at Evanston Northwestern Healthcare, echoed Dal Canto’s fears of paralysis due to encephalitis.

“The patient’s peripheral nerves are affected, which affects all muscles of the body,” he said.

The elderly are most susceptible to encephalitis, with the youngest casualty in Illinois being a 49-year-old male.

Dr. Gary Noskin, an associate professor at Feinberg School of Medicine, said the West Nile patients he came into contact with were often confused and disoriented.

“They weren’t able to tell which year it was,” he said.

Dr. Stuart Johnson, also an associate professor at Feinberg, said the virus causes muscle weakness, similar to the effects of polio. But because West Nile encephalitis attacks the victim’s brain tissue instead of the spinal cord, it is more dangerous than polio.

Encephalitis also is damaging because doctors only can deal with symptoms and not the root problem, said Tom Schafer, a spokesman for the Illinois Department of Public Health.

West Nile is relatively new to the American continent, so it has provided little data for study. The mosquito-borne illness first reached the East Coast of America in 1999. It only has been in Illinois for two years.

With 738 cases and 48 deaths in the state, this year’s epidemic is the worst outbreak of a mosquito-transmitted disease since 1917, when 2,300 cases of malaria were recorded. This year’s national total stands at 3,559 cases with 211 deaths from West Nile virus.

Scott offered encouragement, saying there is a high possibility the virus will not be as widespread next summer.

“Once you’re hit one year, it will be mild the next,” she said.