AsianScientist (May 27, 2011) – A long-term study of the epidemiology, genetics, and antigenic properties of swine influenza virus in Hong Kong has found an increase in viral diversity in live pigs over the past three decades.
The study also attributed the increase in viral diversity to increased transportation of live pigs across geographical borders, allowing swine flu viruses from different locations to mix and thereby increasing their diversity.
Since the majority of human swine flu infections have been a result of close contact with farm animals, this increase in diversity may have increased the risk of swine-to-human transmission. While the pigs had no symptoms or very mild undetected symptoms to most viruses isolated for the study, scientists don’t know how virulent these viruses can be in humans.
Dr. Vijaykrishna Dhanasekeran, a researcher in the Emerging Infectious Diseases Program at Duke-NUS Graduate Medical School in Singapore, and the lead author of the study published online in Nature on May 25, said:
“This means that the repertoire of viruses that humans are in contact with everyday has increased and this may lead to a higher likelihood of swine-to-human transmission, although the risk remains unquantified.”
“It is important to monitor viruses in swine, especially those that can emerge in humans that we do not have antibodies for,” Dhanasekeran added.
The researchers also discovered that two major lineages of H1 subtype viruses and the human H3N2 viruses were frequently detected in swine. Several combinations of the three lineages were detected in pigs, including some avian (bird) viruses, showing that there is an inter-transmission of influenza A viruses among birds, pigs, and humans.
The researchers analyzed data collected from more than 650 samples taken from swine from 12 years of surveillance, together with 34 years worth of other data on swine flu viruses.
The study, the longest of its kind, involved researchers from Duke-NUS Graduate Medical School in Singapore, the University of Hong Kong and Shantou University Medical College in China, St Jude Children’s Research Hospital in the United States, and the University of Oxford in the United Kingdom.
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Source: DukeHealth.org.
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