Are Swine Flu Fears Overblown?

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Some virologists already had doubts when the WHO first announced the existence of a new flu in late April. Top health officials were indeed talking about a "new subtype" of the influenza virus, one feature required by the US Centers for Disease Control and Prevention to meet its definition of a pandemic. But "new subtype," it turns out, was an inaccurate description—the pathogen behind swine flu is in truth only a new strain of an old subtype. And as influenza expert Hans-Dieter Klenk at Marburg University's Virology Institute explains, "such strains are more closely related to each other than subtypes are."

Today's swine flu did arise new from a combination of avian and swine viruses. But it's related nonetheless, in a roundabout way, to the pandemic-causing virus of 1918, which still has descendants circulating in the population. That could help explain why older people contract swine flu considerably less often than young people—for their immune systems, this new virus is simply an old familiar one retooled. But younger people may also be less defenseless against the new virus than originally believed.

The influenza proteins H1 and H2, which characterize different viral subtypes, typically vary by more than 40 percent. The H1 protein that has made the leap from pigs to humans with the current swine flu virus, however, differs from the H1 of the seasonal flu virus by only around 25 percent. "And we suspect," Klenk explains, "that this closer relationship is also reflected in some way on the immunological level." What does all that mean? That unlike with the pandemics of 1918, 1957 and 1968, when truly new subtypes sent waves of infection across the globe, this time human immune defenses may be better prepared.

The fact that many people require only one vaccine dose to be protected against swine flu is one piece of evidence. Another is that the virus didn't spread nearly as far through the population as originally feared during the Australian winter.

No one knows how swine flu's course will run. But in the end, British molecular biologist Derek Gatherer may prove to have been right all along. Gatherer declared his suspicions back in the beginning of July, that humankind is facing only a "pseudo-pandemic," one that "may be insufficiently virulent ultimately to enter the annals of major pandemics."

Translated from the German by Ella Ornstein

Provided by Spiegel Online—Read the latest from Europe's largest newsmagazine

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