Daily Flu Counts

The bad news is that cases of novel 2009 influenza A(H1N1) continue to increase. Data from WHO Epidemic and Pandemic Alert and Response (EPR), Influenza A(H1N1) - update 43 — 23 May 2009:

The good news is that the spread appears to be sub-exponential at this point.  Exponential growth will appear linear on semi-logarithmic axes.  Here I plot the natural logarithms of these same case-count data against the date. We can see a distinct (negative) concavity, indicating that the growth in confirmed cases is sub-exponential.  The usual caveats about under-reporting and the lag between infection and reporting dates apply, but this is a modicum of good news.

The austral flu season will be heating up (as it were) soon enough. Once again, it seems only prudent to me that the richer nations of the north help poorer nations, who are about to get hit, with efforts to contain the spread of novel A(H1N1).  Given the relative genetic homogeneity of this novel strain, choice of a strain to include in a vaccine is straightforward (if a little late for the beginning of the northern flu season).  If we can minimize the intensity of antigenic drift (despite the name which might imply random change, this is directional selection away the ancestral antigenic type in the presence of multiple circulating strains) by minimizing the number of cases in the south during their flu season, perhaps we can dodge the bullet of an extremely high-mortality pandemic.

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