Bad Lyme Bug Spreading
Virulent Strain of Lyme Disease Spreading in U.S., Europe
"What is surprising is these ospC type A strains in the U.S. and in Europe are genetically almost identical," Qiu says. "So this type is quite unusual in its ability to colonize new habitats. ... This is very strong evidence for this type having a very broad ecological niche in terms of the species that can carry it."
"This means it went from one continent to another continent relatively recently," adds Luft. "And it means that, as Europe and U.S. have very different ecosystems, this strain is highly adaptable to new environments. ... This makes it a formidable foe -- and it causes significant disease."
It's not clear whether this bad Lyme germ traveled from North America to Europe or vice versa. And it's not clear when this happened, although it seems to have occurred in the last 200 years, possibly when a tick-infested bird crossed the Atlantic.
It's likely, Qiu says, that this strain will continue to become more prominent in areas where Lyme disease is established.
CDC medical epidemiologist Kevin Griffith, MD, MPH, says that while Lyme disease has been reported in nearly every state, 10 mostly Northeastern states account for 92% of cases.
Although the 20,000 cases reported to the CDC in 2006 were fewer than the 23,000 cases reported in 2005, Griffith says the true number of cases is probably larger.
"There is probably a true increase in the number of cases," Griffith tells WebMD.
The good news, he says, is that there's been a drop in the most severe, late-stage manifestations of Lyme disease. He attributes this to doctors identifying the disease -- and beginning treatment -- sooner now than in the earlier years of the epidemic.
Qiu and colleagues report their findings in the July issue of the CDC's Emerging Infectious Diseases.
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