-The new Swine flu, H1N1 virus may have a longer period of infectivity than previously thought. This is according to a study presented at the Interscience Conference on Antimicrobial Agents and Chemotherapy.
The current US Centers for Disease Control and Prevention guidelines have recommended that patients with flu should stay at home for only one day after their fever resolves. Patients with Swine flu were thought to be infectious for only up to seven days.

· Researchers report in one study that up 19% of the people infected with H1N1 influenza appear to shed the virus for up to 16 days. In a second study, 10% of patients with H1N1 flu were shown to have persistent viral shedding for 10 days.

· Viral shedding is the continued replication and release of virus. Viral shedding is an indication of the ability to transmit the infection. These studies indicate that H1N1 may continue to be infectious for an extended period of time and a longer period of time than was previously felt safe to return to work.

· These studies question the current recommendation of the ideal isolation time for Swine flu infections. If people prematurely return to work they may be unknowingly spreading the infection and perpetuating the pandemic.

Cristopher Geiler, M.D.

Reference
49th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC): Presentations K-1918a and V-1269c. Presented September 14 and 15, 2009.