Flu outbreak points to risk from ill co-workers

Working while sick led to outbreak

In the first weeks of the 2009 H1N1 pandemic, a physician became ill at a Chicago hospital and tested positive for the virus. Then other healthcare workers became ill and tested positive — an outbreak that began at a time when the virus was not widespread in the community.

An investigation, reported in Infection Control and Hospital Epidemiology, revealed an interesting pattern: The transmission was occurring among co-workers, not from or to patients. Even if healthcare workers took precautions to protect patients, they were getting each other sick.1

Prevention of influenza transmission "is not 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 Division of Healthcare Quality Promotion at the Centers for Disease Control and Prevention (CDC).

The transmission might have stemmed in part from a misguided sense of devotion to their jobs. More than half (55%) of the infected healthcare 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. "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 [healthcare 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.

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

The hospital ultimately controlled the outbreak with some strict infection control measures. Access to the hospital was restricted to a single entrance near the Emergency Department. Healthcare workers were required to wear surgical masks in most clinical areas. The hospital also cancelled all non-essential meetings and asked employees to report to the employee health staff for screening for influenza-like illness.

By mid-May, 83% of the hospital's 1,721 employees had been screened for symptoms. About 95% of those received prescriptions for oseltamivir for prophylaxis. The outbreak then subsided.

At this early stage of the H1N1 pandemic, no vaccine was available. But the CDC recommends vaccination as the primary method of preventing transmission of influenza. However, the CDC also emphasizes other measures, such as ensuring that healthcare workers do not report to work while sick.

"All health care personnel should be getting their vaccine, but there is more to do: identifying patients who are ill, practicing appropriate hand hygiene, taking sick leave when appropriate," says Kuhar. "All of these things are important in reducing the transmission of influenza. Ultimately, you need a comprehensive approach."

A July 22, 2001, advisory from the American Hospital Association (AHA) gives the push toward mandatory vaccination of healthcare workers another surge of momentum. The AHA stated: "To protect the lives and welfare of patients and hospital employees, the American Hospital Association's Board of Trustees recently approved a policy supporting mandatory patient safety policies that require either influenza vaccination or wearing a mask in the presence of patients across health care settings during flu season. This policy aims is to achieve the highest possible level of protection."2


  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. Infect Control Hosp Epid 2011; 32:611-615.
  2. American Hospital Association. AHA endorses patient safety policies requiring influenza vaccination of health care workers. Quality Advisory 2011. Accessed at http://bit.ly/s41vL2.