Suspect TB, protections failed, HCWs infected

Lessons of an outbreak

The basic premise of worker safety is to provide layers of protection. If each layer is sufficiently flawed, the protection is compromised. That is the lesson of a recent Health Hazard Evaluation in an Arizona hospital, where 18 employees had a TB skin test conversion in 2011 and one employee developed active tuberculosis.

The hospital-associated outbreak began in January 2011 when a patient came to the emergency department with respiratory symptoms but wasn't placed in an airborne infection isolation room. A nursing assistant working in the ED would later develop active tuberculosis, but that diagnosis also was delayed. The employee complained of cough and shortness of breath on March 8 but wasn't diagnosed with TB until May 11.

The first line of defense, recognizing the possible symptoms of tuberculosis and promptly placing those patients in an airborne infection isolation room, had failed. In fact, 10 of the 18 employees with a TB conversion had worked during the original patient's stay when the patient was not in isolation.

"The problem really occurred when that index patient was not in isolation and employees did not know they needed to wear respirators," says Maria de Perio, MD, medical officer with the Hazard Evaluations and Technical Assistance Branch of the National Institute for Occupational Safety and Health (NIOSH). She investigated the cases with industrial hygienist R. Todd Neimeier, MS, CIH.

Granted, this was an atypical case of tuberculosis. The patient actually came to the hospital because of a fall, says de Perio. She had non-specific symptoms and did not have the classic signs, such as night sweats, unexplained weight loss and cough with bloody sputum.

However, the NIOSH investigation also found that employees were confused about the differences between latent TB infection and active TB. Their TB training occurred as a part of overall infection control training. "We recommended improving training to the hospital staff to educate them about the typical and atypical symptoms of active TB and the risk factors for active TB," she says.

Is it really negative pressure?

Numerous other factors contributed to the outbreak. Electronic door pressure monitors had not been re-calibrated since they were installed 12 years before. When the NIOSH investigators checked them, six of the 18 rooms were not operating under negative pressure.

There's a simple way to check that a room is under negative pressure, says de Perio. "You basically just hold a tissue and open the door. If the tissue is blown in, that means the air is being sucked in and it's under negative pressure," she says.

The doors between the anteroom and the hallway also were often left open, they found.

The hospital used some powered air-purifying respirators (PAPRs) to reduce the need for fit-testing. But the investigation found problems with the fit-testing and the use of N95s. Almost a third of the 39 employees interviewed (12, or 31%) reported they had worn a respirator they weren't fit-tested for sometime during their employment.

Investigators observed two fit tests. In one, the employee failed to place the straps correctly, but wasn't corrected by the fit-tester. The fit-test exercises weren't timed and the aerosol (saccharin) wasn't replenished, as necessary.

There were also problems with the TB screening program. In 2010, 16% of employees failed to return to have their skin tests read. From 2007 to 2011, compliance with TB skin testing ranged from 71% to 94% for employees with face-to-face patient contact and 34% to 93% for employees without face-to-face patient contact.

Why you need an EH professional

Better oversight of the TB program would help prevent transmission, the NIOSH investigators advised. In fact, at this hospital, which had about 1,000 employees, the infection preventionist was stretched thin. There was no employee health professional.

"She was responsibile for infection control for the whole facility (inpatient and outpatient), and she was also responsible for everything related to employee health, not just TB-related. We thought it would be a good idea to separate out these duties," de Perio says.

In this case, nursing assistants were the most likely to have a TB skin test conversion. They were the employees who often spoke to patients when they arrived in the ED, and in this hospital they worked in close contact as interpreters.

Using respiratory hygiene, including providing face masks to patients who are coughing, could help prevent transmission, says de Perio.

"CDC has good recommendations for preventing transmission of TB in health care facilities," she says. "Facilities should be aware of that and know those well. It's great to have a written policy, but it's also important to make sure that policy is carried out, as well."

[Editor's note: Infection control tools and guidelines can be found atwww.cdc.gov/tb.]