He added that health policy-makers must balance the economic impact of telling people to stay home longer with the medical impact of some potential extra infections.
The current recommendation is intended to decrease the chance of transmitting the virus, rather than to stop it completely, said Dr. Daniel Jernigan, the deputy director of the CDC's influenza division.
"Some people will continue to shed live virus after their fever stops, we know that," he said, but it's not clear that they remain contagious.
In the absence of clear evidence that shedding virus equals infectivity, he said, "we needed to make a policy that was easy to implement proportional to the severity of the virus."
"If we had a virus with a very high attack rate or death rate," he said, "we might have a very different policy."
De Serres did not report support for his study. He reported financial links with GlaxoSmithKline and Sanofi. Lye did not report support for his study or any conflicts.