If the bird flu strain H7N9 emerged in China in March this year, causing infections in about 134 people and killing 43, another novel bird flu strain, H6N1, emerged this May in Taiwan. Unlike the H7N9 strain, the latest one has infected just one person, a 20-year-old woman who presented with typical influenza-like symptoms. What is puzzling is that she had not come in contact with poultry and did not travel outside the country for up to three months prior to infection. This leaves the transmission pathway inconclusive. Yet, there are indications that the source could be poultry as the H6N1 strain has been endemic in poultry in Taiwan since 1972. Strengthening the possibility of the source is the prevalence of the virus with the same mutation (G228S substitution in the haemagglutinin) in poultry as the one isolated from the woman. If the H6N1 virus with the particular mutation was found in a few chicken in Taiwan since 2000, it became widely prevalent since 2005. As in the case of other bird flu strains, the mutation that gave H6N1 the ability to infect humans originated from a reassortment, possibly of the H5N2 and H6N1 viruses. Besides the unknown transmission pathway, the concern is the unknown causal factor that made the six close contacts of the woman develop a respiratory-tract infection or fever.
The fact that there is only one case of confirmed infection and that the woman has responded well to treatment indicate the strain has not yet acquired transmissibility and lacks the lethality required to cause a pandemic. Yet, H6N1 underlines the inevitability of strains emerging and acquiring the ability to jump from its animal host to humans. The Taiwan virus turns the spotlight on the need for laboratory studies to assess the virulence and transmissibility of possible influenza viruses that may emerge through reassortment. The controversial research earlier by two groups of scientists who undertook experiments to create H5N1 mutant viruses in the lab very nearly divided the scientific community in 2011. The experiments were undertaken to understand possible ways in which the H5N1 virus might mutate and spread in humans. Such experiments were opposed on biosafety and biosecurity considerations. But these concerns have been allayed, with the U.S. Department of Health and Human Services introducing a review process before funding any such research. While it is currently reviewing experiments on H7N9, H6N1 may possibly be the next candidate.
The article has been edited to incorporate the following correction:
“New bird flu strains” (Editorial, Dec. 5, 2013) wrongly said the bird flu strain H7N9 emerged in China in March last year. It should have been March this year – 2013.