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This award-winning blog supplements the articles in Hospital Infection Control & Prevention.

Underestimated? HCW-to-worker flu transmission

We have been preaching to the proverbial choir in this space about protecting frail patients from influenza, but what about immune competent coworkers? A fascinating outbreak during the first weeks of the H1N1 pandemic in 2009 reveals that health care worker-to-worker transmission may be occurring more than commonly suspected, as these infections may typically be assumed to be community acquired.

A recently published report details an H1N1 outbreak in a Chicago hospital in which the index case may have been a physician. The doctor became ill and tested positive for the virus. Other health care workers began getting ill and also tested positive. Tellingly, the hospital outbreak unfolded at a time when H1N1 was not yet widespread in the community.

The investigation revealed an interesting pattern: The transmission was occurring among co-workers, not from or to patients. Even if health care workers took precautions to protect patients, they were getting each other sick.1

In fact, two health care workers who developed H1N1 reported always wearing an N95 respirator or surgical mask when entering a patient room with a patient with respiratory illness.

Prevention of influenza transmission “is not [just] about patient to provider, it’s about transmission from person to person. You really need to take a comprehensive approach to preventing the transmission of influenza,” says David Kuhar, MD, medical officer with the Centers for Disease Control and Prevention’s Division of Healthcare Quality Promotion.

The transmission may have stemmed in part from a misguided sense of devotion to their jobs. More than half (55%) of the infected health care workers reported coming to work one or more days after developing flu-like symptoms.

“This paper serves as a reminder as to what we should be doing for infection control for influenza,” says Kuhar, who commented on the paper but is not one of the authors. “There need to be institutional strategies to prevent transmission of influenza. Showing up to work sick is not good for your coworkers and your patients.”

The study’s authors note that health care workers had “multiple exposure opportunities” to their ill co-workers. “For example, some [health care worker] cases reported traveling to a clinic together by car prior to illness onset. In addition, resident physicians attended daily morning reports and noon conferences,” the authors said.


1. Magill SS, Black SR, Wise ME, et al. Investigation of an outbreak of 2009 pandemic influenza A virus (H1N1) infections among healthcare personnel in a Chicago hospital. infection control and Hospital Epidemiology 2011; 32:611-615.

Michele Marrill

Special update from our sister publication, Hospital Employee Health