H1N1-like virus has potential to transmit efficiently to humans and cause pandemic, study warns after tests on animals in 10 provinces

An overseas study shows an influenza virus strain commonly found among pigs in China has the potential to transmit efficiently to humans and urged governments to take immediate action to prevent an outbreak.

The study published on Monday by the Proceedings of the National Academy of Sciences of the United States of America said the swine flu virus, identified as the Eurasian avian-like H1N1 strain, were found in 139 of 36,417 pigs taken for tests from 10 provinces.

This strain has been circulating in pigs since 1979 and is different from the H1N1 strain that caused the 2009 flu epidemic, researchers said.

The researchers found that the Eurasian avian-flu like H1N1 strain was preferentially bound to human-type receptors, and nine of the 10 tested viruses could be transmitted in ferrets by respiratory droplets.

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“After long-term evolution in pigs, the EAH1N1 SIVs have obtained the traits to cause a human influenza pandemic,” they said.

Researchers found that only 3.6 per cent of children aged below 10 and 13.4 per cent of the elderly aged 60 or above had antibodies against one of the two subgroups of the Eurasian avian-like H1N1 lineage. No adults have antibodies against this subgroup.

None of the children, adults or the elderly has antibodies against the second subgroup, they said.

Their study also found other subtypes of flu viruses, including the H1N1 and pH1N1 strains, in another 89 of the 36,417 pigs tested between 2010 and 2013.

[The H1N1 swine flu epidemic in 2009 broke out in 214 countries and killed 80 people in Hong Kong. Photo: EPA] The H1N1 swine flu epidemic in 2009 broke out in 214 countries and killed 80 people in Hong Kong. Photo: EPAThe Department of Health said today that it was aware of the study and that it had been monitoring influenza in pigs in the city.

“The Centre for Health Protection will maintain close liaison with the World Health Organisation, mainland and overseas health authorities to monitor the latest developments of new types of flu viruses globally,” a department spokesman said.

“It will also adjust Hong Kong’s strategy and health surveillance accordingly when necessary.”

The department said that flu viruses, after undergoing significant genetic change, can mutate into a form that can cause major pandemic in humans.

“Since humans have limited resistance to new types of viruses, they can spread more quickly and widely than ordinary seasonal flu viruses,” the spokesman said.

Results of a flu virus surveillance programme on pigs by the Centre for Food Safety showed that no H5N1 strain of swine flu viruses were found in 4,079 pigs in Hong Kong taken for tests between February and October.