Flu pandemics may return & mutating strains: Studies

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Be prepared: Say scientists

Scientists have warned that we have not seen the end of H1N1 swine flu that swept the globe in 2009/10. The strain of the virus could easily morph into a more transmissible form, while an older, mid-20th century virus could also come roaring back they say. Asian influenza, a H2N2 strain, first appeared in 1957 and killed one to four million people despite a major vaccination campaign. Studies have shown that most people today aged 50 or older retain some immunity to the virus, which continues to circulate in birds and swine. But the younger are more vulnerable they warn.

Gary Nabel, a researcher at the Vaccine Research Center of the U.S. National Institutes of Health and lead author of a commentary published Thursday in Nature said, “H2N2 looms as a public health threat, and could re-emerge.” Governments, the World Health Organization (WHO) and drug companies “should develop a pre-emptive vaccination programme,” he urged.

Between 2003 and 2007, the authors tested 90 people for antibodies to H2N2 viruses. “Our study suggests that people under 50 have little or no immunity, and resistance dramatically increases for those over 50,” they write, while cautioning that the findings need to be replicated in much larger numbers of people. “The low mutation rate for H2N2, and evidence of waning human immunity, make it likely that an H2N2 pandemic could arise from animals,” they explain.

He suggests strategies for anticipating a resurgence of the bird-borne virus.

  • Manufacture the same vaccine licensed in 1957 and immediately inoculate enough of the world's population to provide what scientists call a “herd immunity” to the rest.
  • Stockpile the same vaccine in the event of an outbreak, or make “master lots” and step up production at the first sign of an outbreak.

He urges authorities to be forewarned and suggested that acting now would be far more cost effective than waiting for the strain to reappear. A flu pandemic costs the United States 71 to 167 billion dollars.

Dr Wendy Barclay, Chair in Influenza Virology at Imperial College, says the H2 flu virus does pose a credible pandemic threat, as do other strains of bird flu. But she believes there are some big questions about whether a pre-emptive vaccination programme would be welcomed by the public.

“Now we are in the calm after the storm of that swine flu pandemic, it is timely to open up the debate about pre-pandemic vaccines. As Dr Nabel himself points out in his article, we have to ask whether the public will want or accept a vaccine against a disease that does not at the moment exist…Work towards making such vaccines available is ongoing in many laboratories around the world…Scientifically we are in a position to be able to offer a good solution, the issues to be decided are of cost and of public attitude,” she said.

Richard J. Webby, director of the World Health Organization Collaborating Center for Studies on the Ecology of Influenza in Animals and Birds, based at St. Jude Children’s Hospital in Memphis, commented, “There is little doubt that H2 viruses pose a pandemic threat and a defendable argument can even be made, as Dr Nabel and team have done, that they pose more of a threat than many of the other subtypes of influenza viruses circulating in birds…Although we have not specifically identified an H2N2 virus in our surveillance efforts in birds for a number of years, H2N3 and H2N9 viruses are not uncommon. There is little evidence that global swine populations are major reservoirs of H2 viruses, but they are occasionally reported.” He added that any virus with H2 hemagglutinin is a potential threat.

Michael T. Osterholm, also welcomed the commentary as an important warning. “I think it’s a reminder that just as we were surprised by H1N1 returning, we shouldn't be surprised by the potential for H2N2 returning. I think in this case, [Nabel] has really provided a very important perspective,” said Osterholm, who is director of the University of Minnesota Center for Infectious Disease Research and Policy, publisher of CIDRAP News.

Mutating strain

In another study, published in the online science journal PLoS One, researchers at MIT in Boston led by Ram Sasisekharan identified a single mutation of the 2009 H1N1 virus that would greatly boost its ability to spread among humans.

He explained that this is what happened to the original H1N1 strain, which first emerged in the fall of 1917 in a mild form before coming back nine months later in a far more deadly variant, a two-wave pattern typical of flu pandemics. It was known as Spanish flu and it killed at least 50 million people - three percent of the world’s population at the time. Most of the deaths were due to absence of antibiotics.

Sasisekharan said, “There is a constant need to monitor these viruses.” The swine flu -- so named because it was first identified in pigs in Mexico - has killed some 18,500 people since emerging in the spring of 2009, according to the WHO.

Dr. Ananya Mandal

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.


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