A triple reassortment strain of an H1N2 virus, with genes from avian, swine and human flu, has been shown to jump easily via air to mammals.
The emergence of the H1N1 influenza virus that leapt from pigs to humans in 2009, triggering a global pandemic, reminded us of the need to monitor animals such as pigs that can host the development of dangerous viral strains.
A study published today re-emphasizes that need. Young-Ki Choi at Chungbuk National University in Cheongju, South Korea, and his colleagues have isolated a new strain of H1N2 influenza from Korean pigs that kills infected ferrets — the model animal of choice for influenza work — and can spread through the air.
“It shows that there are very nasty viruses being generated in swine,” says Robert Webster of the St. Jude Children’s Research Hospital in Memphis, Tennessee, one of the study’s senior authors. “And these viruses are coming out of apparently healthy pigs.”
Like that responsible for the 2009 pandemic, the new strain, known as Sw/1204, is a ‘triple-reassortant’ virus — that is, one with genes from avian, swine and human flu. Such viruses, which first appeared in North America in 1998, have been circulating in Korean pigs for at least a decade.
Choi wanted to assess the pandemic potential of Korean strains. His team tested two H1N2 and two H3N2 viruses isolated from pig abattoirs before the 2009 pandemic. Most of these viruses did not cause any signs of serious disease in ferrets.
Sw/1204 was the exception. It replicated in the airways and lungs of three infected ferrets, killing one and causing such severe disease in the others that they had to be euthanized. The virus also spread through the air to infect three healthy ferrets that were housed in cages next to infected ones.
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