Getting schooled in the flu

Researchers at Stanford University wanted to learn more about how influenza spreads. So they went back to high school -- literally.

It’s long been known that the flu and other infectious diseases, including whooping cough and SARS, can spread via the tiny droplets people produce when they cough or sneeze. It’s also well known that people are more likely to come in contact with these infected droplets when they’re in an enclosed environment with many others -- an environment, say, like a high school.

But not as much is known about the patterns of how diseases spread within such communities.

To study how that process unfolds, the Stanford team outfitted 788 students, teachers and staff (94% of the entire school population) at one U.S. high school with wireless sensors that recorded who had contact with whom during a “typical school day” during the 2009 swine flu outbreak.

In that single day, they recorded 762,868 encounters at a distance of 10 feet or less. (Such close proximity would permit transmission of illness, the researchers reported.) Most of the interactions were short -- less than a minute. “Mixing patterns” followed the flow of the school day, with more contacts recorded during high-activity periods, such as the breaks between classes and at lunchtime.

The group used the data they collected to simulate how the flu might have spread through the school, if introduced by a single infected person. They reported that their simulation was “in very good agreement with absentee data from the influenza A (H1N1) spread in the fall of 2009.”

They also reviewed thousands of scenarios to examine the best interventions to prevent the spread of disease, including immunization or social distancing strategies. They found that unless you have information about contacts similar to that the Stanford team collected, targeted strategies are unlikely to work any better than random ones. Attempts to immunize the most popular students or teachers, for example, didn’t prevent disease any more effectively than random immunization did.

Being popular, it seems, isn’t all that.

The research was published in the Proceedings of the National Academy of Sciences.