New Deer Tick Virus causes permanent brain damage in 50% of cases

"The first clue that deer tick virus could cause human disease came in 2001 when deer tick virus RNA, taken from the brain of a man who died ... in Lyme-endemic areas, many, if not all, cases previously diagnosed as POWV are likely deer tick virus. Furthermore, the number of cases appears to be rising rapidly."

Encephalitis-causing Ticks Emerging in Northeast

Marc El Khoury, MD, with New York Medical College in Valhalla, New York, reported on two related diseases: deer tick virus, which, as its name suggests, is carried by the hard-bodied deer tick, and Powassan virus (POWV), which is carried by a soft-bodied tick that feeds on groundhogs and woodchucks.

But the two diseases share a common ancestor and are difficult to tell apart in standard antibody tests.

Until recently, however, deer tick virus was not considered a threat to human health. The first clue that deer tick virus could cause human disease came in 2001 when deer tick virus RNA, taken from the brain of a man who died in 1997 shortly after a presumed Powassan encephalitis infection, was sequenced.

Now, El Khoury reports that, in Lyme-endemic areas, many, if not all, cases previously diagnosed as POWV are likely deer tick virus. Furthermore, the number of cases appears to be rising rapidly. Between 1958 and 2003 -- a span of 45 years -- only about 40 cases of POWV were reported in the United States and Canada. Then, in four years, from 2008 to 2012, 21 cases were reported from Wisconsin and Minnesota, and 12 cases from New York State.

"Almost all of these cases are in Lyme country, where humans are much more likely to be preyed upon by deer ticks carrying deer tick virus than ticks carrying Powassan virus," El Khoury said. "Now it appears that in Lyme-endemic areas, people can not only get Lyme disease or babesiosis, but also a deer tick virus-related meningoencephalitis."

Many infections are probably mild or asymptomatic. But more severe infections can progress to encephalitis, which can have a case fatality rate of up to 15 percent and cause permanent nerve or brain damage in about 50 percent of diagnosed cases. Powassan virus infections (that may in fact be deer tick virus) have been reported in Pennsylvania, New Jersey, Massachusetts, New York, Connecticut, Maine, Vermont, Minnesota, and Wisconsin.

Full article here-  http://www.sciencedaily.com/releases/2012/11/121112135510.htm