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Monday 24th June 2019

Researchers track swine flu source

31st May 2011

Pigs imported from Europe and North America into China seem like a probable source for the swine flu virus, according to a recent study by researchers in Hong Kong, China, and Singapore.


The researchers monitored flu viruses in pigs over a period of 12 years, and concluded that the most lethal flu virus, against which humans have no immunity, originated in Europe.

Southern China has the largest swine population in the entire world.

Vijaykrishna Dhanasekaran, assistant professor at the Duke-NUS Graduate Medical School's Program of Emerging Infectious Diseases in Singapore, said that Eurasian and North American flu viruses had entered pig populations in southern China and replaced the earlier viruses since about 2001.

He said that the practice of importing pigs for breeding purposes had increased in southern China over the past 20 years, since farmers wanted to improve the quality of their stock.

Since 1998, the researchers have collected more than 650 samples of flu virus from about 800 blood samples.

After the researchers had taken the viral samples, they compared the pathogens to those found in Europe, North America, and Asia.

Surprisingly, all of the viral specimens belonged to just three lineages.

The most dominant flu virus was the Eurasian avian-like H1N1 virus.

The second was North American in origin, and had been circulating in pigs since the 1990s.

The third, the H1N1 swine flu virus, has been circulating in China and abroad for over 80 years.

Dhanasekaran said that scientists now had a better understanding of the way viruses traveled around the world.

He said that the Eurasian avian-like H1N1 virus would be a particular problem, since the human immune system had not developed any antibodies against it.

The way viruses have spread means that people's overall viral exposure is greater than it would have been in a past era, but the researchers are not certain if this affects people's level of risk.

However, the fact that there are so many viruses may increase the probability that specific viruses have the opportunity to mutate into human-transmissible forms.

Dhanasekaran said that viral diversity varied geographically, and that he believed researchers should conduct surveillance and target specific viruses.

The researchers hope that understanding the way viruses evolve may help humans to spot viruses that are best able to spread to humans, to soften the blow of the next pandemic.


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