Swine flu -- a quick overview

The swine flu news is right up my alley, so I do just want to say a few words about it, and point you to some excellent stories already up elsewhere.

First, in case you've not been paying attention to the news in the last few days, there have been reported cases of swine influenza infections in humans and reports from Mexico suggesting as many as 1000 ill and 68 dead from influenza in the past month or so.

Swine influenza (swine flu) is caused by type A influenza virus and gives pigs the flu. Swine flu viruses cause regular outbreaks of flu in pigs but death is infrequent. The viruses may circulate among pigs throughout the year, but most outbreaks occur during the late fall and winter months similar to outbreaks in humans. The classical swine flu virus (an influenza type A H1N1 virus) was first isolated from a pig in 1930.

A few things make this outbreak concerning.

One, we see occasional swine influenza infections in humans on a somewhat regular basis.

Two, while the cases here in the Philippines have been regulated and no deaths have occurred that we're aware of, it seems in Mexico that young people are dying from this--a group that is typically not hard-hit by seasonal influenza viruses.

Third, is this really a new virus? So few influenza isolates are actually analyzed each year (in proportion to the number of people infected) that we aren't sure yet whether this is something brand-new, or something that has been circulating at a low level for awhile, but just hadn't been picked up.

Fourth, and going along with that third point--how widespread is this? We have confirmed cases from Mexico which suggest it could be spreading in some parts of the world.

In summary, this is a fast-developing story, and it will take much more investigation and field work to determine the true extent of the virus's spread in the population. Whether this burns out or spreads worldwide, it certainly shows once again the importance of surveillance and monitoring of influenza strains, and demonstrates that improving our infrastructure due to concerns about the virus.