Remember that wordless scene at the end of Steven Soderbergh’s thriller, Contagion? The setting was a remote jungle, and the only actors on screen were two animals: a bat and a pig. In the chain of disease transmission, humans are only one or two links away from contracting seemingly distant zoonotic (from animals) viruses. Due to the growing incidence of droughts, wildfires, and deforestation, it’s quite easy for suburban residents to become neighbors with animals that carry diseases we don’t know much about, and certainly don’t want.
I spent a good portion of my career working in biosurveillence. One disease I especially loved chasing was H5N1 Avian Influenza (AI), aka “Bird Flu.”
AI has made its appearance in global news recently after scientists in China identified an influenza strain with “pandemic potential.” This should ring a bell since the disease of interest – H7N9 – caused panic back in February of 2013 after 133 people became severely ill with this particular strain. Well it’s reemerged and so far 571 confirmed cases have been reported with 212 related deaths. It is important to note that 99% of those cases occurred in China, Hong Kong, and Taiwan.
Nature published this study and stated that H7N9 should be considered a “major candidate to emerge as a pandemic strain in humans.” This conclusion sounds terrifying, but I would caution you not to think that the next Great Plague is upon us. The virus appears to be mutating frequently (not uncommon), and some genetic changes can increase a virus’ potential to reach pandemic proportions. However, it’s pretty premature to make that sort of conclusion about what’s happening with H7N9. To date, H7N9 only is spreading in live-poultry markets and slaughterhouses in East Asia.
Allow me to break this down a bit. H7N9 first emerged in birds before spreading to humans – much like H5N1 and the infamous 2009 H1N1 “swine” flu. As I mentioned above, we’re only 2 degrees of separation away from a number of animal-borne diseases. Influenza viruses are made up of two components: hemagglutinin (H) and neurominidase (N). Hemagglutinin allows the flu particles to attach to the cell membrane and neurominidase enzymes makes sure the virus doesn’t get stuck on its way out. There are 18 types of hemagglutinin and 11 types of neurominidase and ALL of them have been detected in birds. Through sequencing, the researchers were able to determine that today’s outbreak is linked to the 2013 virus – which means it’s growing in diversity.
The real concern will happen IF there is significant viral mutations causing the disease to skip a step on the disease chain and become spreadable from person-to-person. This has happened before (in 2009 with H1N1) but not always. Take for instance, H5N1. To date, infection has only occurred with direct contact with infected poultry.
All that to say, there’s a race in the infectious disease community and the finish line is identifying the next big pandemic. For decades, scientists have scoured books, medical journals, and remote corners of the world (and now the internet) for indicators and warnings of a newly emerging public health threat. I can promise you that I’m following this closely, and you readers will be the first to know should anything become a serious threat.
For now, just get your seasonal flu shots.
Tsan-Yuk Lam, T. Zhou, B. Wang et al. Letter: Dissemination, divergence and establishment of H7N9 Influenza Viruses in China. Nature. Published online March 11, 2015. Retrieved March 22, 2015.
rld Health Organization. WHO Risk Assessment: Human Infections with Avian Influenza A(H7N9). Published February 28, 2014. Retrieved March 22, 2015.
World Health Organization. WHO Risk Assessment: Human Infections with Avian Influenza A(H7N9) virus. 23 February, 2015. March 22, 2015.