Just last month the Centers for Disease Control and Prevention declared victory over canine rabies in the United States -- a fatal virus that kills 55,000 people a year globally.
That declaration may have been premature.
A growing demand for overseas dogs -- many from countries where the disease is endemic and the animals are too young to be vaccinated -- has put rabies back on the government's radar and caused the CDC to go to work on stricter rules aimed at imported dogs.
As many as 300,000 puppies a year are being imported, based on early estimates, according to G. Gale Galland, veternarian in the CDC's Division of Global Migration and Quarentine.
Driving the import trend is the demand for puppies, rather than older dogs that have behavioral or health issues.
The Border Puppy Task Force in California estimates that 10,000 puppies entered San Diego County from Mexico in just one year. Some only a few weeks old are sold for $1,000 each in shopping center parking lots on the street.
"Most people don't think about this deadly disease," said Dr. Nina Marano, director of the regulatory unit at the CDC. "People take for granted that their dogs are not at risk."
Just this spring, a puppy from India got a clean bill of health from officials at Seattle Tacoma International Airport. Days later, at its destination in Alaska, the dog was diagnosed with rabies, according to Washington's Veterinary Board of Governors, which is investigating the case.
In 2004, Los Angeles saw its first case of rabies in 30 years with a puppy imported from Mexico. In Massachusetts, a dog imported from Puerto Rico -- a U.S. territory where stray dogs are rampant -- was diagnosed with the disease.
In response to this trend, the CDC has pledged to strengthen regulations that were written long before the burgeoning pet resale market.
So far, no humans have been infected from rabid dogs, but health authorities say that without preventive action, it's only a matter of time.
According to the World Health Organization, rabies is still common in much of Latin America, Eastern Europe, India and other parts of Asia -- regions where puppies are raised for commercial resale in the United States.
Under current regulations, puppies under 12 weeks of age are allowed to enter the country as long as they are kept in isolation for 30 days and later vaccinated.
Rabies is typically transmitted to humans through the bite of an infected animal. In the United States, rabies in domestic animals has declined dramatically since the 1950s, though it still exists among raccoons, foxes and bats.
Rabies is easily preventable by a vaccine, but the virus is virtually impossible to treat once symptoms begin.
The only known survivor of the disease was a Wisconsin girl who was bitten by a bat and was put into an induced coma in 2004. All other recent attempts to treat three other victims in the United States and one in Canada failed, and all four died.
Since the 1950s, travel rules have relied on the responsibility of individual dog owners, not international traders, said the CDC's Marano. Enforcement has been lax and inconsistent from state to state.
"We've been considering changing the regulations for quite some time when we realized there had been a change in the way people bring their animals into the U.S.," she said.
There are a number of factors at work, according to both breeders and rescue operations. In the last decade animal rights groups have effectively convinced the public that breeders are politically incorrect. As a consequence, breeders are producing fewer litters.
At the same time, many parts of the country have done such a good job of animal population control that there are no adoptable puppies in shelters. Also, say CDC officials, unregulated Internet sales and smuggling of international pets is on the rise.
The majority of dogs - 33 percent - are acquired through a friend or adopted as strays, according to the American Pet Product Manufacturer's Association. Another 27 percent come from breeders and 10 percent from shelters.
Patti L. Strand, president of the National Animal Interest Alliance (NAIS), a consortium of pet owners, breeders and veterinarians, said it's the newer shelters and rescue groups who are most involved in "humane relocation."
Strand said that only two years ago, when NAIA began researching the issue, foreign imports on shelter Web sites varied in age. "Today, most of them are puppies," she said. "It's is easy to speculate that … enterprising rescuers and shelter directors could help developing countries become breeding grounds for stocking U.S. shelters."
A hobby breeder, Strand worries that the practice could "diminish the responsible breeding and placement of well-bred, healthy dogs and cats."
Other animal rights groups say adopting overseas makes no sense when 4 million unwanted dogs are put to death each year.
"We are obviously barely coping with our own overpopulation crisis," said Daphna Nachminovitch, director of People for the Ethical Treatment of Animals (PETA), who said many animal shelters face little regulation, and budgets for animal control are strained.
"If a shelter is empty, it's not doing its job," said Nachminovitch. "I can take you anywhere in this country and on streets are homeless, unsprayed animals with litters. I talk to people in the trenches every day. Their doors are not wide open enough."
Even though dog overpopulation is rampant in some states, particularly in the South, successful spaying and neutering programs in the Northwest, California and the Northeast have created a dearth of adoptable puppies, say local shelters.
One rescue group -- Save a Sato (Spanish slang for mixed breed) -- has brought an estimated 14,000 dogs from Puerto Rico to the United States since its founding in 1996, according to Massachusetts volunteer Twig Mowatt.
The island is home to thousands of abandoned and abused dogs in need of homes.
"It's a beautiful thing," said Mowatt, who herself adopted a terrier named Rico. "People are really desperate for an adoptable dog, and they don't want to go to pet stores or breeders. Otherwise there would be nothing."
In Massachusetts, where many of these dogs are adopted by shelters, puppies must be held for 48 hours before being released to homes to watch for signs of illness.
But protocol failed in 2004, when one puppy was diagnosed with rabies during quarantine at a shelter in Cape Ann, Mass. The puppy -- only several months old -- developed neurological problems consistent with rabies and was euthanized, according to Donna Rheaume, a spokesman for the state department of health.
A state lab confirmed the animal had rabies, she said, and all who had handled the dog were given preventive treatment.
Shelter Inc. of Sterling, Mass., accepts two or three Puerto Rican dogs a month for adoption. The shelter also takes local animal control surrenders and seeks out dogs who need homes from states like Tennessee and Virginia.
"We have much higher protocols than picking them off the street and throwing them on a plane," said director Leigh Grady, who even took in a puppy from Thailand after the 2004 tsunami.
"That dog had books of medical history," she said. "He had a better medical passport that I did."
The shelter charges $350 for puppies, a fee that covers the costs associated with transportation and medical care. The shelter also carefully screens its adoptive families.
"Everyone wants to help, especially if they can save an animal that was abused," said Grady. "They went the breeder and pet store route and they want to do the right thing."
Meanwhile, the CDC said it is not opposed to importing animals, rather it hopes stricter regulations -- now in review and expected to take effect next year -- will continue to do what it has hailed as one of the greatest public health successes of the last half century -- eliminating canine rabies.
"If animals are being imported responsibly, that's OK with us," said Marano.
Still, she said, about working with shelters and rescue operations, "Let the buyer beware."
"It is safe in the U.S. because we work very hard to keep rabies out," said Marano, a practicing veterinarian. "But you always have to be careful. Pick the brightest puppy in the bunch and not the runt -- the one that looks healthy and has a good disposition, and some sort of health certificate from the pound."