Public Health

Morning Rounds: Updates on Swine Flu and Cookie Dough

As public health workers know too well, most battles against microbes are more tense negotiation than flame war — the goal isn't to eradicate the bug necessarily, but to find and contain it, all the while hoping whatever treatment you throw at it doesn't make things worse. Today's headlines — with updates in the investigations of contaminated cookie dough and swine flu — are notes from the barricade.

First, the cookies: FDA officials yesterday searching the Nestle plant in Danville, Virginia turned up a package of refrigerated dough that does, indeed, contain E:coli 0157:H7. They're still awaiting genetic confirmation that it's the same strain that's made at least 59 people across the U.S. sick, but that seems very likely.

The central mystery continues: How did the E.coli get into the mix? We've all been told for years not to eat raw dough—but that's because of the risk of salmonella, a relatively frequent bacterial passenger on the shells of raw eggs. E.coli, an intestinal bug from cattle, is a surprise. Officials yesterday told reporters that a careful check of the plant workers and equipment turned up no traces of the bacteria. The dough ingredients—eggs, milk, flour, chocolate, and butter — have never been thought to harbor E.Coli. Today's Washington Post quotes the FDA's David Acheson:

It raises the likelihood that it was an ingredient. And it really means that industry has to be constantly vigilant, because foods we think of as low risk could be contaminated with a deadly pathogen.

Translation: Your cookies may be safe, but the FDA's turning up the heat on manufacturers.

Meanwhile, lab workers in Denmark are reporting the first known case of swine flu that is resistant to Tamiflu, the main anti-viral drug that governments have been stockpiling in case this strain of H1N1 turns nasty this summer. The single case of drug resistance is worth noting but not yet cause for alarm, according to the CDC. NPR's Richard Knox sent this background note to explain why:

"It's not good. But experts say it doesn't necessarily mean all or even most swine flu viruses will soon become resistant to the mainstay antiviral.

The Danish patient reportedly has recovered from the flu. And as far as anyone knows, he or she did not pass the resistant virus on to anyone else.

Experts have been worried swine flu might become Tamiflu-resistant because many of the ordinary seasonal flu viruses that circulated in North America this past season were unfazed by the drug. One of these unfazed seasonal strains is also from the H1N1 family.

Roche, which makes Tamiflu, says the Danish patient's virus had only one genetic mutation, called H-274-Y. That mutation has long been known to arise in the viruses infecting a small percentage of people on Tamiflu, in response to treatment. But here's the difference: The Tamiflu-resistant seasonal flu virus has a half-dozen mutations, including H-274-Y. Scientists don't know if the swine flu virus can or will acquire this suite of resistance mutations.

Actually, it's pretty surprising that the pandemic virus hasn't acquired the H-274-Y mutation more often, given the thousands of people treated with Tamiflu lately.

"It's certainly likely that we will see this in the United States," says Dr. Carolyn Bridges of the Centers for Disease Control. But so far the CDC has tested almost 200 swine flu viruses for Tamiflu resistance and hasn't found any.

One reason, Bridges says, is that the new H1N1 virus has an "N1" gene that's very different from the corresponding gene of the seasonal H1N1. That's significant, because Tamiflu works by blocking neuraminidase —- that's what the "N" stands for. So maybe the pandemic virus's N-gene isn't as susceptible to the Tamiflu resistance mutation as the analogous gene in its very distant cousin, the seasonal H1N1 virus.

But the Danish case shows that it can happen.

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