By Maggie Fox, Health and Science Editor
WASHINGTON (Reuters) - Federal health experts declared a small victory against a fatal and untreatable virus on Friday, saying canine rabies has disappeared from the United States.
While dogs may still become infected from raccoons, skunks or bats, they will not catch dog-specific rabies from another dog, the Atlanta-based U.S. Centers for Disease Control and Prevention said.
"We don't want to misconstrue that rabies has been eliminated -- dog rabies virus has been," CDC rabies expert Dr. Charles Rupprecht told Reuters in a telephone interview.
Rabies evolves to match the animals it infects, and the strain most specific to dogs has not been seen anywhere in the United States since 2004, Rupprecht said.
While the incubation period for rabies is as long as six years in humans, it is only six months in a dog.
"Even though we still live in a sea of rabies and even though we have rabies viruses circulating among raccoons and foxes and bats, the dog rabies virus, which is the most responsible for dog-to-dog transmission and which is still the greatest burden to humans ... it is that virus that has been eliminated."
Rabies kills 55,000 people a year globally, according to the World Health Organization. It is easily prevented with a vaccine, but many people do not realize they have been infected and once symptoms begin to show, it is almost impossible to treat.
Only one person -- a Wisconsin girl who was put into an intentional coma in 2004 -- has ever been known to have survived rabies infection.
Rupprecht said attempts to treat three victims in the United States and one in Canada have failed. The victims all died.
The virus can infect virtually all mammals, but like most viruses it evolves and can be "typed" genetically. Species-specific strains are well characterized for bats, raccoons and skunks for instance, as well as for dogs.
"A dog rabies is very different from a skunk rabies virus," Rupprecht said.
While cats are susceptible, Rupprecht said there is not a known rabies strain specific to domestic cats.
Mandatory vaccination has created what is known as herd immunity in U.S. dogs, Rupprecht said, and it will be vital to continue this to protect dogs -- and people -- from the virus.
"The elimination of canine rabies in the United States represents one of the major public health success stories in the last 50 years," CDC Director Dr. Julie Gerberding said in a statement.
"However, there is still much work to be done to prevent and control rabies globally."
Canine rabies is still very common in many countries, including much of Latin America, sub-Saharan Africa, India, China, the Philippines and elsewhere.
Some island nations such as Japan, New Zealand, Barbados, Fiji, Maldives, and Seychelles are rabies-free.
Greece, Portugal, Norway, Sweden, Uruguay and Chile are also free of rabies.