But a scientist for the Centers for Disease Control and Prevention said the federal agency has not seen any evidence that the virus is causing a different type of brain damage. He said doctors may be seeing more-serious cases this year because there are more cases overall. But he acknowledged that the CDC does not collect the granular data needed to quickly determine whether the virus is causing more-severe brain damage.
Still, Angus, who has treated West Nile patients for a decade, and Leis, who has more experience treating severe West Nile illness than perhaps any doctor in the country, both suspect the virus has changed — a view bolstered by a Texas virologist whose laboratory has found signs of genetic changes in virus collected from the Houston area.
“I’ve been struck this year that I’m seeing more patients where the brain dysfunction has been very much worse,” said Angus, of Detroit’s Henry Ford Hospital. “It makes you wonder if something’s different, if something’s changed.”
And while the virus in the past has typically invaded the brain and spinal cord only of people who have weakened immune systems, such as the elderly and transplant or cancer patients, Angus this summer treated a severely affected woman in her 20s and a man in his 40s.
Leis said he is seeing much more severe encephalitis — inflammation of the brain — than he has in the past. “It is clearly much more neuroinvasive, neurovirulent,” he said.
Four patients Leis treated this summer had lost their ability to talk or write. Another was paralyzed on one side, as often seen in strokes, not West Nile infections. Others experienced recurring seizures.
In all, 11 of the first 12 patients Leis saw this year at the Methodist Rehabilitation Center in Jackson had more severe brain damage than he had seen previously. The outlook for such patients varies, but most will face years or a lifetime of disability.
“For the first time, we have radiographic evidence, clinical evidence of the virus attacking the higher cortical areas,” said Leis, who has published 15 scientific papers describing previous West Nile patients.
Marc Fischer, a CDC epidemiologist who tracks the West Nile virus, said the agency has not noticed the changes described by Leis and Angus. “There’s just a lot more cases this year than anybody has seen in at least 10 years,” he said. “You’re just going to see more severe cases and probably a broader variety of manifestations.”