As swine flu keeps spreading, researchers reveal more of its story

With all my traveling and move preparation, I hadn’t been keeping up with the latest on swine flu (aka the new H1N1 strain) — and truth be told, I figured the threat of a pandemic was water under the bridge. Not necessarily, as I learned by listening in to a press conference earlier today.

In fact, 6,552 cases have now been reported, but an estimated 100,000-plus people are infected – and about 42,000 children remain home from schools that are experiencing high infection rates.

Anne Schuchat of the Centers for Disease Control and Prevention said she hopes people will still take good care to avoid spreading the flu – avoiding travel over Memorial Day if family members are sick — and warned that the current outbreak could be far from over.

“It could keep circulating through the summer, and it could come back in the fall in the worst way,” she said.

The press conference was held in conjunction with the expedited release of a new paper in the journal Science that uncovers the origin of the latest pandemic threat, found by analyzing 70 samples from infections in Mexico and the United States. 

Lead author Rebecca Garter, a scientist affiliated with the World Health Organization and the CDC, and 58 co-authors report that the new H1N1 strain represents a North American triply merged flu strain – a 1990s combination of human, swine and avian varieties – that swapped genes with a Eurasian strain.

The two types had gotten together before, “but in Asia, not in North America, and not with same gene constellation,” said Nancy Cox, a flu researcher at CDC and a study co-author, who also spoke during the press conference.

From a human health perspective, the good news is that part of the newly emerged swine flu shares with human seasonal flu strains a susceptibility to at least some kinds of antiviral medications. And laboratory ferrets vaccinated against current human seasonal strains didn’t get sick from the new swine strain.

But it’s too soon to say whether those same vaccines will work in the more complex immune systems of people.

Cox said researchers are still trying to figure out the details of the virus’ jump from swine to humans – and the possibility hasn’t been ruled out that there was some intermediate host.

Asked what that host might be, Cox was able to offer no examples. (Personal opinion/speculation alert: an attempt to placate the hog industry?)

Research leading to new vaccinations and stockpiles is also ongoing, boosted by a recent $1 billion pledge from Kathleen Sebelius, secretary of health and human services.

Meanwhile, both Cox and Schuchat emphasized that increased surveillance of influenza in pigs should be a priority. Swine flu has circulated in the world’s pigs for decades without causing much trouble — and so its evolution has gone under the radar compared to the better studied human and avian strains.

“Surveillance in pigs does occur when there is an outbreak that causes disease, but the surveillance is not systematic,” Cox said. “Farmers don’t report outbreaks in pigs.”