Earlier today, I pointed out with some thumping of the ol' chest that the CDC has indirectly confirmed my theory of late April regarding swine flu; namely, that we could compare this event with the 1946-47 pandemic/epidemic of H1N1 and the 1951 H1N1 severe epidemic to see if there was a correlation.
The New York Times article was the first confirmation of that. Now, the AP has also written on the topic. But their story is more precise in the age group (persons ages 60 and above) that seem to have natural antibodies against 2009's swine H1N1.
A simple subtraction of the number 60 from the number 2009 (or 2008 if you prefer, since the virus apparently first manifested itself in September 2008 in Mexico) yields the number 1948. This is so close to the 1946-47 severe epidemic that it cannot be considered coincidence.
As I have mentioned many times previously, the 1946-47 epidemic may have, in fact, been a pandemic of influenza. It was certainly an epidemic, and was by accounts as severe, illness-wise, as the 1957 H2N2 "Asian flu" pandemic, with roughly the same mortality, which was serious but not apocalyptic.
Textbook research shows that flu seasons had been relatively mild from 1930 until 1946, when all viral Hell broke loose. A serious antigenic event -- a huge drift, or perhaps a more likely antigenic shift due to reassortment of human flus -- took place. It rendered vaccines useless (sound familiar?) and started a new chain of H1N1 flu that culminated in yet another antigenic seismic event in 1951. That virus caused more epidemics until it was deposed by H2N2 in 1957.
It is highly unlikely that antibodies to pre-1946 influenza are helping seniors today. In my own opinion, it must have been the 1946-47 strain of H1N1. And that would seem to indicate a swine background for that mutation, but I will leave that for the researchers.