Pssst, Swine Flu is Still Here

The coming Aporkalypse appears to have faded into last week's obscurity. With WHO raising the pandemic alert from 3 to 5 in the span of about 24 hours, it seemed that Oinkmageddon was upon us.  But now it's hard to find a news piece on swine flu, let alone an inflammatory one. This is something that worries me and lots of other public health professionals. Not so much the lack of inflammatory new pieces. More, I worry that people are going to see this incident of just another case of health officials needlessly pushing the panic button.  There is always the possibility that the public health measures enacted to control extensive spread of Influenza A(H1N1) may have actually worked! The epidemic fizzling when the alert goes to level 5 is really the best possible case, right? Alas, I doubt that it's really the case.  As I noted before, it seems unlikely that we will have extensive sustained transmission in the northern hemisphere at this late date. But case counts continue to grow globally and the austral flu season starts in the not-too-distant future.  

WHO publishes case counts each day, and I have plotted them from 30 April through 13 May.  These are the worldwide confirmed cases as of this morning.

WHO worldwide confirmed A(H1N1) cases as of 14 May 2009We can see that the case count does, in fact, increase each day and shows no sign of slowing down. This is true, incidentally, whether one plots the cumulative number of the incident number -- clearly this plot is more dramatic, but the incidence does not show any obvious sign of decline. Of course, there is an inherent lag in the reporting of confirmed cases, so it is at least possible that the number of cases has peaked.  But I doubt it.  Recent analysis by an international team of epidemiologists suggests that the reproduction number (the average number of secondary cases produced by a single primary case in a completely susceptible population) is substantially greater than that of seasonal flu.  The reproduction number tells us how fast and how far an infectious disease will spread and how many people will ultimately be infected and higher values of the reproduction number mean faster, further and more. This team also found that the estimated case fatality ratio is less than that of the 1918 pandemic strain but comparable to the 1957 pandemic strain.  So, given proper environmental conditions for transmission, this variant of the flu looks like it could spread rapidly, widely, and cause a decent amount of mortality.  It seems entirely possible that this is exactly what will happen in the southern hemisphere in the coming months, after which it will come back and hit here in the north.

As I noted before, I can hope is that people have not become inured to warnings of epidemics because of our recent experience with H5N1 bird flu and this new H1N1 swine flu (there is also the last swine flu scare of 1976).  Some saner press coverage would help. Of course, it would mean less grist for the mills of John Stewart and Stephen Colbert, but it might mean a public better prepared for a potentially real public health emergency that we still may face.

3 thoughts on “Pssst, Swine Flu is Still Here”

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