Now, researchers say, the big questions include, When is it best to close schools? And what are the downsides?

The study, reported in the journal Clinical Infectious Diseases, looked at what happened in two Texas communities during the H1N1 "swine" flu epidemic of 2009. In one community, schools were closed as a precaution; in the other, they weren't.

It turned out that in the district where schools shut down, there were fewer ER visits for the flu.

What's more, among kids age 6 and up, there was no increase in flu-related ER trips, while that rate doubled in the community where schools stayed open.

"The effect was most dramatic among school-age children," said Dr. Martin S. Cetron, of the Centers for Disease Control and Prevention (CDC).

There have been skeptics who've doubted that school closures could have much impact during a major flu outbreak, according to Cetron.

"They've said, well, people will just congregate in malls or other public places," explained Cetron, who directs the CDC's division of global migration and quarantine, and worked on the study.

But schools are different from malls, Cetron pointed out, with kids being in close contact with each other all day long.

He said he thinks this study, along with others, "settles" the question of whether school closures are effective. "Should this be an arrow in our quiver? I think the answer is ‘yes,'" Cetron said.

But lots of other questions remain.

"Under what conditions could (school closures) be warranted?" Cetron said. "What level of severity is needed?"

And if schools are closed, he noted, what are the downsides? Parents will have to stay home from work, or find child care. And kids and teachers will have to make up the lost school time somehow. So the expected benefits of school closings would need to be worth the troubles.

PREDICTION IS DIFFICULT

Every year, between five percent and 20 percent of Americans get the flu, contributing to some 36,000 deaths. The elderly and people with chronic medical conditions, like heart or lung disease, are among those most at risk.

But the 2009 H1N1 flu epidemic was noteworthy in that it hit children and healthy young adults hard.

The current study looked at two adjacent counties in Texas: Tarrant County, which closed its schools for eight days after a few kids were diagnosed with H1N1; and Dallas County, where schools did not shut down after a few cases were detected.

Before Tarrant County's school closures, the flu accounted for about 3 percent of all ER visits to area hospitals; during the closures, that rate inched up to just over 4 percent. But the increase was bigger in Dallas County during the same time period: from 3 percent, to just over 6 percent.

The impact was most clear among kids ages 6 to 18. In Tarrant County, there was no increase in the proportion of ER visits blamed on the flu. In Dallas County, the figure more than doubled, from about 5 percent to 11 percent.

"It's important to point out that this was a pre-emptive school closure," Cetron said. "Usually, most closures we see are reactive."

Predicting how a flu outbreak might affect a local area is far from easy. It's not like tracking a hurricane, for instance, Cetron pointed out.

Decisions on school closures are made locally. For school districts to make wise decisions, Cetron said communication with local and state health agencies is key.

SOURCE: bit.ly/Tly968 Clinical Infectious Diseases, online October 19, 2012.

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