June 21, 2010

 

Hong Kong ramps up pig inspection on new virus

 

 

Scientists from Hong Kong are calling for ramped-up surveillance of pig populations after discovering a new swine flu virus that is a hybrid of the pandemic AH1N1 virus and viruses previously found in pigs.

 

The discovery of the virus, found early this year in a pig taken to slaughter in Hong Kong, suggests what experts have feared: the AH1N1 virus may reassort easily with other viruses in pigs.

 

That is a process that could generate new flu viruses that might have the capacity to sicken humans, they warned, noting two viruses high on the pandemic watch list - H5N1 and H9N2 - are occasionally found in swine in Asia.

 

The discovery was reported by scientists from the University of Hong Kong and Shantou University Medical College in Guangdong province, China. It was published Friday (June 18) in the journal Science.

 

It is the first report of a reassortment of the pandemic virus, which in humans has been slow to evolve. Nancy Cox, head of the influenza division at the US Centers for Disease Control said surveillance shows little significant variation in the viruses isolated from people and no need yet to update the virus used to make human flu vaccine.

 

Pigs are called the mixing vessel of flu because they can be infected both by avian flu viruses and by human viruses. When pigs become simultaneously infected with more than one virus, the viruses can swap genes, producing new variants that can pass to humans and sometimes spread among them.

 

One of the senior authors of the paper said the fact the first reassortant involving pandemic AH1N1 has been found in swine underscores the role the animals play.

 

Over the past year, especially in the early days of the pandemic, AH1N1 would have had plenty of opportunities to reassort with human flu viruses in people, researchers said.

 

"It has been in pigs for a much shorter time and as far as we can tell to a more limited extent and already we can detect a reassortant. So it suggests -- although the numbers are very small yet -- that probably it is not difficult really for the pandemic virus to reassort with other pig viruses," said Dr. Peiris, a microbiologist at the University of Hong Kong.

 

Late last October, they started finding pandemic AH1N1 viruses in some of the pigs in their research. Those viruses appeared to be the product of human-to-pig transmission, Peiris explained.

 

But in early January, one of the swabbing forays produced a novel finding - a virus that had internal genes from one line of swine flu viruses, a hemagglutinin from a Eurasian avian flu lineage and the neuraminidase gene from the human pandemic AH1N1.

 

However, there is no evidence the virus is continuing to spread or that it is inherently more virulent than AH1N1.

 

Meanwhile, scientists in the swine flu community have been questioning whether pandemic H1N1, which has been found in pigs in multiple countries around the world, would become established as one of the circulating viruses in herds.