Anybody who hasn’t been asleep for the last few days — anyone who listens to television, reads a newspaper, or checks out news on the internet — knows that a new flu has arrived, and that a lot of public health officials are concerned. The first cases of what is now being called “swine flu” surfaced in Mexico last week, where more than 2000 cases have been reported and as many as 103 deaths are thought to have been caused by the virus. As of Monday, the World Health Organization has confirmed 40 swine flu cases in the United States, twenty of them on Monday. There are going to be a lot more.
The United States declared a Public Health Emergency last Sunday, so that preparations to deal with the possibility of a wide-spread flu epidemic could be facilitated. The emergency declaration lets the government purchase more antiviral drugs, and reposition resources where they will be most effective. One quarter of the national stockpile of 50 million courses of antiviral drugs will be released.
While calling for a heightened state of alert the next day, President Obama emphasized the swine flu outbreak is not a “cause for alarm.” There is still a great deal we don’t know, CDC officials emphasize in interviews with the print and television press. No American has died, they point out, and there is no reason for panic
The good news is that the swine flu virus infecting Americans is not lethal, like the bird flu virus I wrote about in this St. Louis Beacon column last December. It triggers only mild symptoms in most people infected with it. There have been no deaths in this country, and few patients sick enough to need hospitalization. The large number of deaths in Mexico probably reflects a very large pool of infected people, rather than a more virulent version of the virus.
The bad news is that this swine flu virus appears to be highly infectious. Unlike bird flu, which only infects those in direct contact with infected birds, swine flu virus passes easily from one person to another. Visitors to Mexico have already carried it to New York, Texas, Kansas, Ohio, and California as well as Canada, New Zealand, and Europe. With little doubt, the virus will spread rapidly around the world.
In a nutshell, we are confronting the mirror image of last year’s bird flu threat. While bird flu is very virulent, it is not highly infectious. Swine flu is highly infectious but not very virulent.
So why is everybody so scared?
You can get a hint of the reason by looking a little more closely at the swine flu virus. Why SWINE flu? Influenza virus infects three major hosts: humans, birds, and pigs. Said simply, this virus came from a pig. It could as easily been called “Mexico flu,” in much the same way Hong Kong flu and Asian flu were named after their place of origin. Swine flu is just a nickname for this version of the influenza virus.
It has a more formal name, and that’s where the story starts to get a little scary. Like most people, influenza viruses have two-part names. The first part of the name specifies which of 13 distinct types of hemagglutinin (H) protein the virus carries on its surface; the second part specifies which of 9 distinct types of neuraminidase (N) protein is on the virus surface . The Asian flu of 1957, which killed over 100,000 Americans, is H2N2. The Hong Kong flu of 1968, which still kills some 36,000 Americans yearly, is H3N2. The bird flu which has scared so many of us for the last few years is H5N1. The Spanish killer flu of 1918, which killed some 50 million people in 18 months, is H1N1.
So what is the name of the new swine flu? H1N1.
It’s not exactly the same virus, of course. Influenza virus has a very high mutation rate (it makes a lot of mistakes when it copies itself each generation), so that this descendant, when its full DNA sequence is determined, would be expected to have accumulated many differences from the 1918 version.
Still, the name explains a lot. According to the CDC, the 1918 H1N1 virus infected 500 million of the world’s 1.5 billion people in under two years 30% of everybody on earth. That’s infectious. That the 2009 H1N1 virus passes so easily from person to person likely reflects this ancestry. It is easy to imagine H1N1again sweeping over the face of the earth.
And that’s of course what is so scary. When the 1918 H1N1 virus first appeared in early March of 1918, infecting a mess cook named Albert Gitchell at Fort Riley Kansas, it was no more virulent than the 2009 H1N1 cases being reported in the United States this week. By the end of the week in March, 1918, 522 other soldiers came down with the flu, but symptoms (chills and fever) were mild and almost all recovered. In the fall the troops were sent to Europe and the nightmare began. Mutations occurred in the H1N1 virus that increased its virulence. Soon people began to die, all over the world. Over the following two years one person in three became infected, and 2% of these died.
This is the nightmare our public health officials are not talking about out loud. There is no way on earth to know if the 2009 H1N1 will follow the course of 1918 H1N1 and become more virulent, or remain as it is, no more of a problem than the flu we deal with every year.
One thing is for sure. This scare is going to test our ability to develop a new flu vaccine quickly. I would feel an awful lot better if I were told by our government that it was pulling out all the stops to get 2009 H1N1 vaccine produced and widely available. In the meantime, paper face masks don’t seem as silly a precaution as they did a month ago.
If you want a bit more background about all this, I suggest you read my column from last December “Whatever Happened to Bird Flu?”
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