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A Project of The Annenberg Public Policy Center

How Serious Is Swine Flu?

Blogs, news organizations and Twitter are all exploding with rumor and fact about the swine flu outbreak. But at the National Academy of Sciences today, President Obama said there was no need to panic:

Obama: We are closely monitoring the emerging cases of swine flu in the United States. And this is obviously a cause for concern and requires a heightened state of alert.  But it’s not a cause for alarm.

So what’s the real terror alert level on swine flu? Is it time to break out your paper surgical mask? Well, it’s hard for us to gauge the mortality rate of this influenza strain for a couple of reasons. First, though the Centers for Disease Control and Prevention says that samples from Mexico and the U.S. are essentially genetically identical, in practice the cases outside Mexico have all been mild. As of yesterday, in 20 confirmed U.S. cases, there had been no deaths and only one hospitalization. As of this posting, there have been 40 confirmed U.S. cases, but no deaths reported. Geographical factors may be influencing the disease’s severity, making it hard to say how deadly this flu is on its own.

Second, we simply don’t know how many people have had this strain. There have been 149 suspected swine flu deaths in Mexico as of this posting, but out of how many cases? The Associated Press is reporting that 1,995 Mexicans were hospitalized with pneumonia since the beginning of the outbreak; if those were all flu, and there were no other flu cases, that would be a 7.5 percent mortality rate. But mild flu cases often don’t make it to the hospital, meaning that the number of non-deadly cases might be much higher and the death rate proportionally lower.

The most famous flu pandemic, the 1918 Spanish flu, infected 28 percent of Americans and had a mortality rate of 2.5 percent. If swine flu turned out to be equally virulent, that could mean a death toll of 2.1 million in the United States, more than three times the number of deaths in 1918 (when the country’s population was lower). By contrast, influenza typically kills more than 36,000 people per year in the U.S. Those people are usually ailing or elderly, while healthy young people can be at greater risk of contracting pandemic flu.

How likely is it that we’ll see a couple million deaths? It’s hard to judge at this early stage, but medical science has come a long way since the early 20th century, and so has information transmission. We’re already Twittering madly about 40 confirmed U.S. cases, while the CDC is releasing stockpiled antivirals and is at work on a vaccine.

The CDC and the World Health Organization can’t say for sure what the impact of this flu outbreak will be, so neither can we. But as of right now, Obama doesn’t seem to be off base when he says that it’s a cause for concern, not for panic.