The swine flu explained

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The world has found a new strain of flu, so now what? Enter the virus hunters. This pack of epidemiologists, virologists, and infectious disease experts (sounds like a fun party) are fast on the bug’s tail, looking for answers that may help us control its spread. What are they trying to figure out? How long will it take to rustle up some answers? And when you’re an epidemiologist chasing down a flu virus, what do you do in your lab all day?

On "The Takeaway," Dr. Susan P. Fisher-Hoch, an epidemiologist at the University of Texas School of Public Health and co-author of the book, "Level 4: Virus Hunters of the CDC," sorts out the conflicting theories around the recent outbreak.

The nature of the virus, according to Dr. Fisher-Hoch: "The pigs are important, but they’re a little bit of — if you’ll excuse the expression, a red herring — because this particular virus is not a pure swine virus. It’s one-third human virus, one-third bird virus, and one-third pig virus. And the ability of this virus to make itself into new shapes — it kind of shuffles itself like a pack of cards with different viruses — is what causes new viruses to emerge, and that’s what starts pandemics."

She says the H1N1 virus is going to be tough to get ahead of: "The first thing you do with an outbreak is you try to stop it, or at least mitigate it. This one is going to be very difficult to stop because the disease is so transmittable, and by the time it’s been transmitted, you’re behind it — it’s all ahead of you."

And why the swine flu is a pandemic: "We call it a shift in influenza — every year we have drifts … with a drift you have tiny changes, and need a new vaccine every year. But occasionally the virus has a big jump to an entirely new virus, and that we call a shift. And a shift results in a pandemic, and that’s what we … haven’t seen since 1967, so we were kind of overdue for this — it used to happen every ten years or so, and we haven’t had one for 30 years, so we really are overdue.

Dr. Fisher-Hoch explains how the infection occurs: "The thing is this, the influenza virus can infect a lot of species … it’s not really a human virus, but it jumps to humans, and it jumps to pigs and to some other species.

"A single person gets infected with more than one virus at the same time. Those two viruses — which are quite different — get into the same cell. Each virus has eight little pieces of its genome … and when it gets in a cell it takes it coats off, and out pops its eight little pieces. Well if you’ve got two viruses in a cell, now you imagine yourself sixteen little pieces … eight little matching pairs, and then shuffle it like a pack of cards, and you come out with eight and eight, and you will see that you’ve got some different combinations."

"The Takeaway" is a national morning news program, delivering the news and analysis you need to catch up, start your day, and prepare for what’s ahead. The show is a co-production of WNYC and PRI, in editorial collaboration with the BBC, The New York Times Radio, and WGBH.

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