1,000,000 Americans have been Infected with Swine Flu and that's the Good News

06.27.09 | 1 Comment

Well, there is some new information from the CDC today and it contains both good and bad news. Based on statistical modeling, they estimate that more than half a million New Yorkers and probably more than a million Americans have been infected with Swine Flu (novel H1N1/A).

So, where's the good news? Actually, the size of those numbers is very good news for anyone afraid of being killed by this new strain. If we use only the confirmed cases, we get a mortality rate of about 1 in 220. (There are around 28,000 confirmed cases and 127 deaths. Divide the one into the other and you get 220.) Given that estimates tell us that the typical seasonal flu has a mortality rate of 1 in 1000, this simple math would suggest that Swine Flu is about five times as deadly.

But, the new data tell us that there are 1,000,000 cases and 127 deaths. That gives us 1 in 7800 or so. Let's assume a few deaths were missed as well and we round it to 1 in 7000. That means that Swine Flu is actually much less deadly than the typical flu. Going from five times as deadly to one seventh as deadly in the span of one article is pretty comforting, especially given than most of those infected never even needed medical help to survive.

So, what is the bad news? Well, if this virus has spread to 1,000,000 Americans in May and June, it seems like it should spread faster than gossip come winter when (a) more immune systems are comprised by common colds, (b) flu viruses are able to live longer outside of a host, and (c) people spend more time inside with other people. I have not seen any comment from the CDC on the the percent of Americans they expect to eventually be infected, although a study done at Imperial College suggests that "it will affect about one-third of the world's population". That was in early May, but is based on the Mexican outbreak which was further along than the American outbreak at that time. So, the question is whether the one third number is still likely, and these latest data suggest to me that perhaps it is not. This virus does not seem to be stopped by the natural seasonal barrier, and is spreading rapidly even in its early stages. It seems more prudent to assume a likely infection percentage closer to a half.

Still, the article does give hope overall. Earlier data had indicated that over 100,000 Americans could die from swine flu, but the new information suggests a much lighter toll.

Say half of the American population is infected. That's 150 million people. Now suppose that only 1 in 7000 dies. Very bad, but leaps and bound better than your typical seasonal flu. A little division gives us a new estimate of a bit over 21,000 deaths. A grim number still, but we take the good where we can find it.

Wash your hands, people.

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