Swine flu infection of health care workers (or as CDC refers to them, health care personnel or HCP) was of interest early in the pre-pandemic phase for at last two reasons. One was the obvious goal of estimating the risk to front line workers and devising best practices for their protection. Another was the belief, reinforced by the SARS outbreak in 2003, that spread to HCP was an early warning that the virus was easily transmissible from person to person. SARS is a disease where patients are most infectious in the later stages when they are extremely ill, and HCP were among the hardest hit groups. Most flu is transmitted in the community, but the SARS model still seems appropriate for flu viruses like H5N1 ("bird flu") where transmission is rare. Any report that a health care worker has been infected from a bird flu patient is viewed with alarm, possibly suggesting that the probability of transmission has increased. And bird flu was the template upon which pandemic planning was based. So within a few weeks of the outbreak (the first case of novel H1N1 was diagnosed in mid-April), CDC asked state health departments to report any cases of novel H1N1 among HCP. Yesterday they reported the first results in CDC's Morbidity and Mortality Weekly Reports (MMWR):

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