Spreading swine flu
People may be able to spread swine flu even after their symptoms have subsided, according to new research.
A study of Air Force cadets who came down with the flu this summer found that a significant proportion of them were still "shedding" virus more than 24 hours after their fever and other symptoms had disappeared.
Public health authorities have been asking people to stay home from work and school for at least a day after their temperatures return to normal, in an effort to limit the spread of the virus. But the new findings, reported in the American Journal of Preventive Medicine, raise questions about that advice.
The new study involved some of the 1,300 basic cadet trainees who arrived at the U.S. Air Force Academy in Colorado Springs, Colo., on June 25 for a six-week military training program. By July 6, some of the cadets began to experience flu-like symptoms, and two tested positive for the illness. The virus apparently spread during a social mixer; cases peaked 48 hours after the event and dropped off quickly afterwards.
All together, there were 134 confirmed and 33 suspected cases of H1N1 there between June 25 and July 24--one of the biggest outbreaks at a college or university to date. Fever, cough and sore throat were the most common symptoms.
Tests on nasal swabs showed that 31 of 106 --29 percent--of patients with a temperature below 100 and 19 percent of those with no symptoms for at least 24 hours still harbored viable virus. Of 29 samples obtained seven days after the outbreak of the illness, seven -- or 24 percent-- contained viable virus.
While viable virus does not necessarily mean the illness can be transmitted, the findings do raise questions about whether the current recommendations are sufficient, the researchers say. In an email, here's what Catherine Witkop, the lead researcher, said:
"If transmission is still possible when viable virus is present, it could indicate that individuals may be returning to work or school while they are still able to spread the virus to others. The CDC does recommend that in high risk settings (such as health care facilities or child care facilities) or if the severity of the flu increases, organizations may wish to institute longer periods of isolation for those who are ill; findings of our study support the longer isolation period in such settings."
Anne Schuchat of the federal Centers for Disease Control and Prevention says she still believes the current recommendations are sound. She says other studies indicate that the presence of fever is a good way to know if someone is infectious.
October 21, 2009; 7:00 AM ET
Categories: Family Health , General Health , Influenza
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