Sept. 19 (Bloomberg) — Coughing hogs at a 5,000-head piggery in Northern Island are being investigated to determine how they became the latest animal victims of swine flu.

The pandemic H1N1 influenza strain infected about 4,500 hogs at the piggery in Greenhill, U.K. veterinary officials said in a report to the World Organization for Animal Health yesterday. Five pigs died in the outbreak, first noticed Sept. 1, when some of the animals began coughing and lost their appetite.

Chief Veterinary Officer Nigel Gibbens said no known cases of human flu have been linked with the outbreak, which resembles infections in pigs in Canada, Australia and Argentina that have usually caused a mild illness from which swine recover in days. Preventing H1N1 in pigs is important, as they can act as a mixing vessel for flu viruses because they are susceptible to both mammalian and avian influenza strains.

“What is critically important in this situation is good outbreak investigation to develop a better understanding of how the pigs picked up this virus,” the International Society for Infectious Diseases said in a report via its ProMED-mail program. Such a probe “will help determine potential exposures of the pigs and whether this is another instance of the virus traveling from humans, in a reverse fashion, over the zoonotic bridge to infect swine.”

The new H1N1 flu strain, discovered in Mexico and the U.S. in April, has swept across 177 countries in four months. The virus has genetic material from pig, bird and human influenza strains. More is of pig origin, prompting the reference to “swine flu.” The World Health Organization is now referring to the virus as the pandemic (H1N1) 2009 virus.

Bad Press

U.S. Agriculture Secretary Tom Vilsack appealed to the news media on Sept. 10 to stop calling the H1N1 virus swine flu, saying the term hurts sales of pork and adds to losses for hog farmers. The H1N1 virus is not transmitted through properly handled pork, the WHO and other authorities have said.

Countries including China and Russia banned some U.S. pork after the virus began making headlines in April. Russia, the fourth-largest importer of U.S. pork in 2008, lifted most restrictions in July.

About 64 percent of Chinese consumers stopped eating pork during the early stages of the pandemic, and 21 percent still consider the meat dangerous, according to a survey commissioned by the Denver-based U.S. Meat Export Federation.

To contact the reporter on this story: Jason Gale in Singapore at j.gale@bloomberg.net.