New, Fast-Evolving Rabies Virus Found -- And Spreading

Anne Minard
for National Geographic News
May 4, 2009


Evolving faster than any other new rabies virus on record, a northern-Arizona rabies strain has mutated to become contagious among skunks and now foxes, experts believe.

The strain looks to be spreading fast, commanding attention from disease researchers across the United States (U.S. map).

It's not so unusual for rabid animals to attack people on hiking trails and in driveways, or even in a bar—as happened March 27, when an addled bobcat chased pool players around the billiards table at the Chaparral in Cottonwood.

Nor is it odd that rabid skunks and foxes are testing positive for a contagious rabies strain commonly associated with big brown bats.

What is unusual is that the strain appears to have mutated so that foxes and skunks are now able to pass the virus on to their kin—not just through biting and scratching but through simple socializing, as humans might spread a flu.

Usually the secondary species—in this case, a skunk or fox bitten by a bat—is a dead-end host. The infected animal may become disoriented and even die but is usually unable to spread the virus, except through violent attacks.

Skunks have already been proven to be passively transmitting the strain to each other, as documented in a 2006 study in the journal Emerging Infectious Diseases.

Genetic studies suggest foxes are also spreading the new strain to each other, though the results have not yet been peer reviewed.

Unprecedented Evolution

When a skunk in Flagstaff, Arizona, died of rabies in 2001, wildlife specialists thought it was a "freak accident"—due to a one-off, run-of-the-mill bat bite—said Barbara Worgess, director of the Coconino County Health Department.

Lab tests later showed that the virus had adapted to the skunk physiology and become contagious within the species.


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