How worried should we be about the Swine Flu?
The mortality in Mexico is shockingly high: 81 cases out of 1300, or about 6%. The great Spanish Flu pandemic, on the other hand, had a mortality of about 2.5%. Normal rates for flu are less than a tenth of 1%, with most of those deaths occurring in people who are already weak: children, the elderly, the immunocompromised. The Spanish Flu hit hardest the 15-34 age group, who seem to have been done in by their own strong immune response. It's not clear which pattern this flu follows.
But mortality is not the only consideration; transmissability also matters a great deal. Something like 25% of Americans ultimately got Spanish Flu. But animal viruses usually aren't that efficient at moving from human to human. And the quicker and deadlier a virus is, the less likely it is to spread--the victims die before they can pass it on.
At first glance, though, this one seems to have gotten pretty good at passing from human to human. A few days after we first hear of it, it's in New Zealand, Hong Kong, Spain, the US. To be sure, we don't have large troop movements from the area of infection, thoughtfully bringing it home with them. Nonetheless, with modern travel, if it is transmissable, it will be nearly impossible to stop. Hong Kong is implementing strong quarrantine measures--but Hong Kong is a small island.
The bright side is that mortality here seems to be a lot lower--nonexistant so far. People living in poorer countries tend to have weaker immune systems for the obvious reasons. And the strain that's arrived here may just not be as deadly as the one still in Mexico.
Still, this seems more worrying than SARS was, and SARS was pretty worrying. And if it gets much bigger, it will deal a heavy blow to an already struggling world economy, because this will have deep impacts on global trade flows.