H7N9: The Current Influenza

By Satesh Bidaisee, Associate Professor of Public Health and Preventive Medicine, St. George's University
April 17, 2013

Birds for MPH blogOf all the letters in the alphabet, the two that have no doubt kept the interest of the health care fraternity and indeed is much ado about something are the letters H and N. In meaning, they stand for the names Hemagglutinin (H) and Neuraminidase (N) respectively. Both H and N are two proteins found on the surface of some viruses and in particular the influenza viruses. The history of the influenza viruses and indeed H and N can be referenced in the 1918/19 flu pandemic that accounted for an estimated 40 million deaths among people. This result interestingly accounted for more deaths than those in World War 1. Influenza H5N1 in several outbreaks since 2003 totaled 566 confirmed human cases and the deaths of 332 people. An H1N1 pandemic was also linked to more than 284,500 deaths worldwide between 2009 and 2010. And, more recently, an H7N9 strain has been associated with a number of cases in a localized outbreak at this point in time. The lack of evidence of person to person transmission so far for H7N9 reduces its pandemic potential but to this date, more than 70 persons including 14 deaths have been confirmed with having this flu strain.

The H7N9 experience is new, the number of cases is low and the virus does not appear to be capable of person to person transmission. The investigations to this point established the source of the virus to originate from an avian reservoir. The mechanisms for the resulting H7N9 suggest that the influenza virus is evolving by the swapping of genes between strains. As the virus strives to select H and N strains to become more successful in which the outcome can be a threat of a deadly flu pandemic. Or in the other hand, the resulting strains may not be pathogenic and essentially fade away. The current H7N9 experience reflects a strain as a product of triple re-assortment virus from a mixture of genes from three different flu strains found in Asian birds. This adaptation of viruses in mammals is of concern and can lead to further adaptation on the part of the virus itself.

The response to this H7N9 outbreak has been effective in that communication has been the key to identifying the virus, reporting cases, treating with the reservoir bird population and efforts targeted at mitigating the spread to exposed humans. Beijing and major eastern Chinese cities are taking precautions to limit the spread of the outbreak. One inescapable reality in addressing the outbreak is that a time sensitive, collaborative and multidisciplinary approach by all stakeholders involved is essential to reducing the impact of H7N9 and similar influenza viruses that have occurred and other influenza viruses that will occur in time.

Dr. Satesh Bidaisee is an associate professor and deputy chair of the St. George’s University Department of Public Health and Preventive Medicine.

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