The world is no longer in phase 6 of influenza pandemic alert. We are now moving into the post-pandemic period. The new H1N1 virus has largely run its course.
With those words, the Director-General of the World Health Organization finally deescalated the 2009 H1N1 influenza situation out of pandemic mode last week. If it feels like this is a bit late – after all, there has been little reported influenza activity by the CDC for many months now – then it’s good to recall that the world does, in fact, extend beyond the borders of the good old United States. By any assessment, the WHO’s retaining the pandemic designation for this long has been conservative, but not unjustified.
Globally, the levels and patterns of H1N1 transmission now being seen differ significantly from what was observed during the pandemic. Out-of-season outbreaks are no longer being reported in either the northern or southern hemisphere. Influenza outbreaks, including those primarily caused by the H1N1 virus, show an intensity similar to that seen during seasonal epidemics.
During the pandemic, the H1N1 virus crowded out other influenza viruses to become the dominant virus. This is no longer the case. Many countries are reporting a mix of influenza viruses, again as is typically seen during seasonal epidemics.
The 2009 H1N1 influenza virus has had the potential (and still does) to mutate into something far more lethal than it has to date. While the overall mortality rates have been low, especially considering that 20-40% of the population was infected over the last year, this is a virus that has a taste for preferentially killing the young and the healthy. As this virus “fades” more deeply into the typical seasonal influenza ecology over the coming year, continued vaccination, prevention and monitoring are of critical importance.
Based on available evidence and experience from past pandemics, it is likely that the virus will continue to cause serious disease in younger age groups, at least in the immediate post-pandemic period. Groups identified during the pandemic as at higher risk of severe or fatal illness will probably remain at heightened risk, though hopefully the number of such cases will diminish.
Unsurprisingly, the influenza vaccine for the coming season is going to include the 2009 H1N1 as one of it’s components. In a couple of months, you’ll be inundated with the following basic advice, but I’ll take the liberty of getting a head start: Wash your damn hands frequently. If you’re coming down with a respiratory infection, limit your contact with others, and don’t hesitate to reach out to your doctor to help with a work note, if need be. And, for fuck’s sake, get your influenza vaccine once they become available in a few weeks – there’s no rational, real reason not to.
All that said, soon influenza won’t be our biggest infectious worry – dengue hemorrhagic fever is making it’s way north from Florida and Mexico. For those who felt that this just-ended pandemic wasn’t painful enough, well… you’ll be getting yours soon.