As swine flu concern seems to be simmering down a little, I want to highlight some of the interesting stories about science that should make a difference in infectious disease science, whether H1N1 turns out to be the next dangerous pandemic or not.

1. Why is the flu seasonal? Honestly, I was thinking about this question, too, but NPR got there first this morning.

Conventional wisdom is that flu transmission is all about physical proximity– more people crowded together inside in the winter helps the virus jump from person to person. But the movement of flu viruses probably has greater roots in how airborne viruses move in colder, drier air, and how we and the viruses respond to those environments.

Viruses are more stable under colder and drier conditions, for one. Secondly, those airborne droplets that we cough and sneeze are much smaller and travel farther. Breathe in droplets from the cold into the warm humidity of the lung, and they sink like boulders. Finally, cold dry air means thick mucous in the respiratory tract, which is harder to clear.

2. I’m also fascinated by the ways that seemingly non-medical tools can help crack medical problems (and a shout out to Suzanne for mentioning this in a comment to my earlier post). The New York Times reported on number crunching with several data sets that don’t actually include biological data, but are looking pretty accurate for predicting the spread of H1N1 or swine flu.

At the heart of his simulation are two immense sets of data: air traffic and commuter traffic patterns for the entire country, and the yield of a whimsical Web site, Where’s George?

Where’s George? was started more than 10 years ago by Hank Eskin, a programmer who marked each dollar bill he received with a note asking its next owner to enter its serial number and a ZIP code into the Web site, just for the fun of seeing how far and fast bills traveled. By 2006, the site had the histories of 100 million bills.

3. How fast and what are the logistics in making an H1N1 vaccine? Yep, we could be looking at two shots for the 2009-10 flu season in the Northern hemisphere. It takes a while to make vaccines, and a lot of the science to speed vaccine manufacture up is still untested. From Scientific American:

“For a number of reasons, it is unlikely that [a swine flu vaccine] will be included in the seasonal vaccine,” Gellin says. “As the seasonal vaccine is currently in the final phases of production, waiting for this additional strain would delay the availability of seasonal vaccine.”

In addition, if the new vaccine requires two doses, it would complicate use of the seasonal vaccine as most (except children vaccinated for the first time) require only a single dose each year. “We may learn something from the clinical trials,” he adds, “but the assumption going in is that a new virus that’s not been seen in people before will require two doses.”