The number of pets in the United States diagnosed with the H1N1 influenza virus continues to grow, according to the American Veterinary Medical Association (AVMA). And in each of the cases, it appears the pets contracted the virus from their owners.

The latest confirmed case involves an 8-year-old cat in southern California. Health officials said the female domestic shorthair started sneezing and had nasal discharge in mid-December -- shortly after its owner became sick with a confirmed H1N1 infection. The cat spent a lot of time on its owners lap, the Los Angeles County Department of Public Health, Veterinary Public Health Program said.

The cats veterinarian took a swab sample, which tested positive for the H1N1 virus and Mycoplasma felis. That is a type of bacteria that can cause conjunctivitis, respiratory disease, and arthritis in more than one joint, health officials said. The California Animal Health & Food Safety Laboratory at Davis confirmed the H1N1 test results.

The cat is now recovering.

Los Angeles health officials said this is the first confirmed case of H1N1 in a local pet. Nationwide, however, several other pets and animals have tested positive for the virus.

In December, a dog in New York contracted the virus. The 13-year-old Bedford Hills canine became sick after its owners had a confirmed case of H1N1.

The dog was lethargic, not eating, and had a temperature of 103.6 when its owner took him to the emergency veterinarian on December 13, 2009. X-rays revealed the mixed breed had signs of pneumonia, health officials said.

Veterinarians treated the dog with intravenous fluids, antibiotics, nebulization, and other supportive care. The dog was hospitalized for 48 hours and is now recovering. Tests revealed the dog did not have canine influenza (H3N8), but did have the 2009 H1N1 virus. The Iowa State Laboratory confirmed that finding.

These cases are the latest in a string of illnesses and deaths in pets and animals linked to H1N1 a potentially deadly virus first reported in late March in central Mexico, California, and Texas

The AMVA has tracked these cases since November, when Iowa health officials confirmed the first case of the disease in a 13-year-old indoor cat.

More cases

Here are some other confirmed cases of H1N1 in pets and animals in the United States and around the world:

• In late December, health officials confirmed the H1N1 virus in some commercial pigs in North Carolina. The pigs showed mild symptoms of the disease after possible exposure to people with flu-like illnesses;

• The Ministry of Agriculture and Food in Russia in December confirmed an outbreak of the H1N1 virus is some pigs in that country;

• The United States Department of Agriculture (USDA) in December confirmed additional cases of H1N1 in some turkeys in Virginia. Other turkeys on that Virginia farm tested positive for the virus in November. USDA officials said a farm worker had previously been sent home with flu-like symptoms. USDA officials said the turkeys were still safe to eat. That case marked the first time heath officials had confirmed the virus in U.S. turkeys. Officials had previously confirmed H1N1 in domestic turkeys in Canada and Chile;

• On December 4, Colorado health officials confirmed two cats -- from different households in that state -- tested positive for H1N1. Veterinarians suspected the cats, ages 10 and 11, became sick after someone in their households contracted the virus. The cats are now recovering;

• In early December, Germany confirmed an outbreak of H1N1 in a commercial herd of 425 pigs. Two pigs died. The source of the outbreak is listed as unknown or inconclusive;

• A 12-year-old cat in Pennsylvania died of H1N1 in early November. The domestic shorthair developed a respiratory illness on November 3, 2009, after four members in the household became sick with flu-like symptoms, the AMVA said. The cat then became lethargic, lost its appetite, and had difficulty breathing. X-rays revealed the cat had pneumonia;

• An 8-year-old female cat in Oregon died from H1N1 on November 24, the states public health veterinarian said. The cats owner had previously tested positive for the virus. When the cat arrived at the veterinarians office, she was hypothermic, dehydrated, weak, and had nasal discharge, and blue-tinged mucous membranes. X-rays revealed the cat had severe pneumonia and fluid in her chest. A nasal sample taken from the cat tested positive for the H1N1 virus;

• In November, France confirmed a cat in that country tested positive for the virus. Health officials said the cat developed a respiratory illness shortly after two children in the household became ill. The cat recovered in six days;

• Preliminary tests for H1N1 in a California cheetah came back positive in November. Final tests later confirmed that finding. Investigators suspect an animal handler was the source of that infection. Four cheetahs in that private zoo developed respiratory problems, including coughing, nasal discharge, lethargy, and decreased appetite. But only one of the cheetahs tested positive for H1N1. There are no reported cases of Influenza A: H1N1 (2009-H1N1) transmission from animals to humans in a zoological setting, The Association of Zoos and Aquariums (AZA) said. Animal collections at zoological institutions, therefore, do not present a concern for public health;

• On November 28, published reports in China stated two dogs in Beijing tested positive for the H1N1 virus;

• A cat in Oregon died from an H1N1 infection on November 7, state health officials said. The cat became sick shortly after a child in the household had flu-like symptoms. Three other cats in the household became sick, but have since recovered. Tests revealed those three cats were not infected with the virus;

• Utah health officials in November confirmed a cat in Park City had contracted the H1N1 virus. The cats owner had previously been sick with flu-like symptoms. The cat is now recovering.

Pigs in the United States, Finland, Indonesia, and Taiwan have also tested positive for H1N1, the AVMA said.

Veterinarians say all these recent cases show its possible for the H1N1 virus to spread from humans to animals, especially those who have close contact with their owners.

What to do

What steps can pet owners take to protect their animals and prevent the spread of this virus?

In an interview with, Dr. Ann Garvey, a veterinarian with the Iowa Department of Public Health, recommended the following:

• Wash your hands frequently;

• Cover your mouth when you cough and your nose when you sneeze;

• Minimize your contact with your dogs, cats, or other household pets if you have any flu-like symptoms.

Pet owners who notice any signs of respiratory illness or other influenza-like symptoms in their animals should contact their veterinarians, Dr. Garvey said.

The AVMA said it will continue to track cases of H1N1 in animals and post its findings on the organizations Web site.