Unfortunately, the man's condition continued to deteriorate, life support was withdrawn, and the man, who also had leukemia and therefore possibly a weakened immune system, died 17 days after he fell ill.
In general, Welch said, encephalitis cases of any sort are few, and labs are not usually able to identify the source, unless it is the herpes simplex virus.
"Since no one has been testing, we really don't know the incidence of deer tick virus, but it can't be very high, because we don't have many cases of encephalitis," he said. "What happens in the future will depend on how many ticks get infected, how easy it is to transmit to people and what percent of people infected get severe disease. It could be that people with normal immune systems are relatively resistant."
Visit the U.S. Centers for Disease Control and Prevention for more on tick-borne encephalitis.
SOURCES: Norma P. Tavakoli, Ph.D., research scientist, Wadsworth Center, New York State Department of Health, Albany; Geoffrey Weinberg, professor, pediatrics, division of pediatric infectious diseases, University of Rochester Medical Center, N.Y.; Peter Welch, M.D., Ph.D., infectious disease specialist, Northern Westchester Hospital, Mt. Kisco, N.Y.; May 14, 2009, New England Journal of Medicine