Trying to Understand Influenza

Those who concern themselves with influenza understand one thing above all others: We know very little and the more we manage to learn the more we understand how very little we know.

One of the world’s preeminent influenza experts, Dr. Jeffery K. Taubenberger and coauthor Dr. David M. Morens wrote a commentary published in the Journal of the American Medical Association [JAMA] titled “Understanding Influenza Backwards”.

It is appropriate to ask how the novel virus might behave epidemiologically in coming months, including the possibility of multiple recurrences or “waves.” Spring circulation of the novel virus in the Northern Hemisphere at the end of the 2008-2009 influenza season inevitably has led to comparisons with events in 1918-1919, which in some settings were preceded and followed by outbreaks of respiratory illnesses.

[snip]

Considering the long and confusing track record of pandemic influenza, it is difficult to predict the future course of the present H1N1 pandemic. The virus’ modest transmission efficiency, the possibility of a degree of preexisting population immunity due to prior cross-reactive viruses and vaccines, and its arrival in the Northern Hemisphere as summer approaches all give reason to hope for a more indolent pandemic course and fewer deaths than in many past pandemics. If summer weather in the Northern Hemisphere slows viral spread, transmission may well resurge again in the fall or winter to create a seasonal wave, but pandemic history suggests that changes neither in transmissibility nor in pathogenicity are inevitable. It will be critical to assess the effect of large-scale pandemic outbreaks in the Southern Hemisphere in the current and coming (winter) months. Once again, influenza is showing its latest tricks and must be watched closely to understand what is happening. It is well to remember that, as Kierkegaard said about life, influenza epidemics are lived forward and understood backward.

The commentary, in its entirety, is quite informative. The closing paragraph makes it clear that it was written prior to the Northern hemisphere’s summer months, of which we are in our last. Since the probable time of writing and now we have learned that wherever children congregate, irrespective of outside temperature, H1N1 spreads.

It is this little snippet that I wish to specifically comment on – beyond my general praise of an excellent and highly informative offering:

[snip]

In the last 200 years, at least, pandemic influenza, a respiratory infection of intermediate transmissibility, has never been able to infect the entire population at once.

Life often has those strangely serendipitous random occurrences, today is a case in point. I have a 45 minute to an hour commute each way to work and I’ve recently begun to listen to audio books on the drive to and from. Today I started The Earth Abides, a classic and groundbreaking offering on several levels.

A quote from chapter one [delivered by an over voice in the print addition]:

“It has never happened”! cannot be construed to mean, “It can never happen!” – as well say, “Because I have never broken my leg, my leg is unbreakable,” or “Because I have never died, I am immortal.”

Hearing those words this morning and then reading the last snippet from today’s JAMA find seemed almost – “meaningful”. Something important. It’s a reminder that we cannot – should not – take anything for granted. We should not presume to know what the future holds – or doesn’t. The very point Drs. Morens and Taubenberger make in their closing sentence in JAMA:

It is well to remember that, as Kierkegaard said about life, influenza epidemics are lived forward and understood backward.

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