Tuesday 6 August 2013

Memories of H7N9....

The Annals of Internal Medicine has an article by Andrew Pavia that summarizes some of the key events in the influenza A(H7N9) virus outbreak earlier this year, asking "Should we be concerned?". The question is not specifically answered, rather we are reminded that H7N9 has the ingredients with which we could bake a very good pandemic.

  1. It faces a population with little or no immunity;
  2. H7N9 seems to be a true pathogen, and while we have likely only seen an ice cube's worth of the iceberg of clinical outcomes, we believe it to be an at least partly-adapted pathogen with the potential for fatal infections;
  3. While some human-to-human transmission has most likely been seen, it was not sustained and therefore was not, earlier in the year, capable of spreading with pandemic efficiency

Dr Pavia also asks, "Are we fully prepared for a pandemic?" In answer to that question, we find the pantry is somewhat bare of the ingredients we'd need to bake an equally good pandemic response. Perhaps better stocked than when SARS came knocking though.

Perhaps I've worn the cake analogy out.

We have a stressed heath system, we face the potential for our key influenza antiviral, oseltamivir, to be outgrown by its target and we still lack robust tests that can be used on the spot (point-of-care tests) and not just by expert laboratories. While we can make a vaccine faster than ever before, those systems that have suitable approval for global use and rapid deployment may still take too long to stave off the effect of a virus travelling at the speed of global interconnectivity.

Over at the International Journal of Clinical Practice, Richard Stein also recaps H7N9, a virus that some expect to rise again in the northern cold months. 

Dr Stein dwells more on the molecular and the error-prone nature of RNA virus replication, reminding us of the ability of influenza to exchange bits of its multipartite genome with any other influenza in the cellular neighbourhood.

Every infection/co-infection increases the risk that a more lethal, or a more innocuous, viral descendent could emerge; but will those changes produce a virus that likes its lot and Chooses Life? More often, it will burn out before we even notice it because its just not fit enough to survive the hustle and bustle life of being on the lam from the host immune police, seeking new and suitable attachments, engaging with the cellular microenvironment, reproducing, replicating and assembling into new bodies and making it's grand exit, nare left, to the next potential virus factory. Its tough out there for a virus.

Finally, Dr Stein reminds us that we, the potential virus factories, play an active role in the success of viral spread. From those few folks with an unexplained ability to super-spread virus to more people than most other folks do, to our need to hang around in groups (cities I think they're called) that are separated by too little distance to prevent that guy over there's sneeze from impacting on your eyeballs. 

Dr Stein wraps up noting that we must always be concious of seeking to understand the transmission triad that underpins any pandemic: the host, the virus and the environment

From what we have seen in 2013 alone, that involves a lot of work, a lot of organising, a lot of clinical and laboratory expertise and capacity...and a whole lot of communication.

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