Don't Panic, It's Just a Pandemic

If it's really something to fear, this flu pandemic seems like it's taking its time.

We first heard about "swine flu" in April. Now we're supposed to call it the new H1N1 strain of influenza A.

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Declaring a pandemic is a big official deal, so big that this is the first global flu epidemic in 41 years (the last one was the "Hong Kong flu" which killed 1 million people). A pandemic is something like a global version of an epidemic, which is a disease outbreak in a specific community or region or population. Health agencies work together worldwide to define the word "pandemic" to avoid controversy over how to make this call, said Dr. George T. DiFerdinando Jr., a physician epidemiologist and professor at the University of Medicine and Dentistry of New Jersey-School of Public Health. Once there is rapid human-to-human transmission, there is no question that a pandemic is occurring, DiFerdinando said. The 1918 Spanish flu was a good example of a rapid pandemic — it spread in a period of four to six weeks across every state in the United States.

This new H1N1 virus preferentially infects younger people. In nearly all areas with large and sustained outbreaks, the majority of cases have occurred in people under the age of 25 years.
In some of these countries, around 2 percent of cases have developed severe illness, often with very rapid progression to life-threatening pneumonia.
Most cases of severe and fatal infections have been in adults between the ages of 30 and 50 years.
This pattern is significantly different from that seen during epidemics of seasonal influenza, when most deaths occur in frail elderly people.
Many, though not all, severe cases have occurred in people with underlying chronic conditions. Based on limited, preliminary data, conditions most frequently seen include respiratory diseases, notably asthma, cardiovascular disease, diabetes, autoimmune disorders, and obesity.
Around one third to half of the severe and fatal infections are occurring in previously healthy young and middle-aged people.
Pregnant women are at increased risk of complications. This heightened risk takes on added importance for a virus, like this one, that preferentially infects younger age groups.
The vast majority of cases have been detected and investigated in comparatively well-off countries. It is unclear if the virus will behave differently and make people more or less sick in the developing world, Chan said.

That 10-year thinking is part of what threw medical experts off in 1976 when a swine flu outbreak emerged in 1976 at Fort Dix in New Jersey. The national response to that event taught some hard lessons about efforts to head off a pandemic. The federal government initiated a vaccination campaign — some 40 million were inoculated. But a pandemic failed to materialize. Instead, some people got sick from something else — possibly the vaccine itself (and some of them died). "Predicting pandemics turns out to be imprecise in the medical and public health community," DiFerdinando said. For instance, many medical professionals expected avian flu to become a human pandemic at some point in the past 10 years, but that has not occurred yet. "If you can figure out what the frequency is [for flu epidemics] — you'd be quite famous," DiFerdinando said.

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Robin Lloyd was a senior editor at Space.com and Live Science from 2007 to 2009. She holds a B.A. degree in sociology from Smith College and a Ph.D. and M.A. degree in sociology from the University of California at Santa Barbara. She is currently a freelance science writer based in New York City and a contributing editor at Scientific American, as well as an adjunct professor at New York University's Science, Health and Environmental Reporting Program.