People who have contracted West Nile virus - even those with some serious neurological complications - can take heart that they will fully recover over time, Canadian researchers say.
In a study of 156 Canadians afflicted with West Nile virus disease, including some who developed potentially fatal meningitis and encephalitis, the average time to recovery was about a year, said principal investigator Mark Loeb, an infectious-disease specialist at McMaster University in Hamilton, Ont.
"If they're infected with West Nile, where they have West Nile fever or they have West Nile virus meningitis or encephalitis, these data can tell them what to expect, that gradually over about a year their mental and physical function generally and on average will return to normal," Dr. Loeb said.
While there is always some variation among individual patients, Dr. Loeb said, "I think at least it helps patients and physicians and their families to know what to expect over time."
West Nile virus is passed to humans by certain species of mosquitoes, which carry the virus after biting infected birds. (David McNew/AFP/Getty Images)
Human cases of West Nile have been recorded in Canada since 2002. The virus is passed to humans by certain species of mosquitoes, which carry the virus after biting infected birds. Between 2002 and 2007, more than 2,200 cases were recorded by the Public Health Agency of Canada in most of the provinces. Saskatchewan has been the hardest hit of all.
So far this year, three cases have been reported - one each in Ontario, Manitoba and Saskatchewan, PHAC's website shows.
The study, which also involved researchers from Alberta, Saskatchewan and Manitoba, was unable to determine the long-term prognosis for patients who developed acute flaccid paralysis related to West Nile. That condition, which results from a defect in the nervous system, causes patients to lose the ability to properly move their arms or legs, Dr. Loeb said.
The study did not include those with West Nile-related paralysis because there were not enough to make clinically definitive conclusions.
"That's one important thing to know for context," he said, noting that further studies will be needed to determine those patients' long-term prognosis.
Over all, Dr. Loeb said, about 80 per cent of people who contract West Nile develop no symptoms and will not know they were ever infected. Of the 20 per cent who do get sick, most will experience flu-like symptoms. Only about one or two in 150 people develop serious complications such as encephalitis.
That was the case for Dennis Tieche of St. Catharines, Ont., who recalls being bitten on Labour Day, 2003. Three days later, he was in hospital after developing high fever, headaches, severe confusion and dizziness.
For close to two weeks, Mr. Tieche was in a coma in intensive care, during which time he was twice put on life support and his family told to prepare for the worst.
But he suddenly emerged from his coma, and began his long recovery.
"It was tough," recalls Mr. Tieche, 64, who could not walk without assistance and took seven months to recover. "I had to learn how to start all over again: walking, you name it."
Five years later, he is physically and cognitively back to normal, he said. "I'm really lucky."
Dr. Loeb said recovery takes longer on average for patients with meningitis or encephalitis than for those with milder symptoms - but all do eventually return to normal if they get over the initial infection.
There is a small subset of patients who die of complications from the virus.
"What's interesting and what surprised us was the fact that there seems to be a lot of resiliency in individuals who had the encephalitis or meningitis or the milder symptoms."
Still, the researchers would like to know why some people are infected but don't become sick, while others get seriously ill.
A study being done in conjunction with U.S. researchers will analyze the DNA of people who have acquired West Nile virus to see if some have a genetic predisposition that makes them more vulnerable to serious complications.
The study is published in this week's issue of the Annals of Internal Medicine.
