Cough and chaos: A false outbreak of pertussis

Cough and chaos: A false outbreak of pertussis

Dartmouth scrambles after pertussis scare

When a day care worker reported to employee health at Dartmouth-Hitchcock Medical Center in Lebanon, NH, with a severe, spasmatic cough that had lasted more than two weeks, an employee health nurse immediately thought of pertussis.

A lab worker reported similar symptoms, and soon there were other cases of concern. Some of them tested positive using PCR tests. The hospital posted advisories about respiratory hygiene and began screening employees and visitors for symptoms. The number of suspected cases rose, many of them conforming to the classic case definition for pertussis.

Within the next few months in the spring of 2006, the employee health department evaluated about 1,700 health care workers — 1,100 of them within a two-week timeframe. With help from volunteer nurses and physicians, they administered 3,599 Tdap vaccines, which had recently been approved by the Food and Drug Administration, covering 72% of the hospital staff in mass immunizations. They gave out 1,364 treatment doses of azithromycin and the lab performed 1,041 PCR tests.

Employees were furloughed, home sick, or working with masks, while the hospital canceled some elective procedures and closed beds.

The efforts were a tremendous success: Dart-mouth-Hitchcock effectively controlled a respiratory disease outbreak. But months later, the medical center received some stunning news. Not a single case of pertussis could be confirmed by culture, and only one case was confirmed through other testing. The New York Times dubbed it "the epidemic that wasn't."

The episode provides some important lessons for pertussis control, outbreak response, and pandemic influenza preparedness. While Dartmouth-Hitchcock hopes to fine-tune its response capabilities, the best decisions were made given the available information, says Robert K. McLellan, MD, MPH, FACOEM, medical director of Dartmouth-Hitchcock employee health and president-elect of the American College of Occupational and Environmental Medicine (ACOEM).

When faced with an outbreak that could prove fatal to vulnerable patients, as pertussis is for infants, occupational health and infection control must work together to implement swift and aggressive controls, he says.

"We're not just talking about a day or two of lost work [for employees]," he says. "We're talking about death as a potential outcome [for some patients]. As a team, we wanted to take this very seriously," says McLellan, who also is chief of the occupational and environmental medicine section at Dartmouth Medical School.

Why you should vaccinate HCWs

The Dartmouth case points out the benefits of pertussis vaccination of health care workers. While other respiratory diseases can cause severe cough, vaccinated employees would be much less likely to acquire pertussis. (The vaccine is about 85% effective.) That would shape decisions about outbreak control measures, says McLellan.

But without vaccination, occupational health and infection control professionals must rely on imperfect diagnostic tests.

Culture is the "gold standard" for detecting Bordetella pertussis, but pertussis is notoriously difficult to grow in culture. "In a medical center where infants may be at risk, you can't wait two weeks to make decisions about how to manage it," says McLellan.

Dartmouth-Hitchcock relied on the swifter PCR test to detect pertussis DNA. "The PCR test has the advantage of being rapid and sensitive. It can detect a small number of organisms being present," says Elizabeth Talbot, MD, New Hampshire deputy state epidemiologist. "However, the PCR is not a standardized or FDA-approved method. There are many different approaches to conducting the PCR test.

"What happened at Dartmouth-Hitchcock is not an isolated event. There are other settings that have struggled with making accurate rapid diagnosis of pertussis," she says.

Dartmouth-Hitchcock acted appropriately, under the circumstances, she says. "We're forced to make a decision about the intervention before the diagnostics return a clear answer," she says.

Occ health needs surge capacity

Perhaps more importantly, the respiratory disease outbreak served as a real-life drill for pandemic influenza. Lesson learned: Hospital employee health will need surge capacity.

It was possible to manage symptom screening, illness evaluation and treatment, mass immunization, employee furlough and a respiratory hygiene program for thousands of employees in a short time-frame — but only with help from nonoccupational health nurses and physicians, says McLellan.

About 55 physicians offered to help and needed just-in-time training on occupational health protocols, he says. The hospital now is considering this as a part of an all-hazards approach — designing its emergency preparedness with just-in-time training of physicians that can be assigned to occupational medicine. "Much of the care could be routinized and any physician could be brought up to speed, but they need to be trained and provided a protocol," McLellan says.

Occupational health needs to work closely with infection control, human resources, and safety to provide a framework for outbreak response. That team, in conjunction with hospital administrators, would form a Hospital Incident Command Structure with the authority to trigger the emergency response and assign doctors and nurses to help occupational health, he says.

"When people think about managing a pandemic, the traditional public health planning focuses on how to take care of the community," McLellan says. "[But] how are we going to take care of our staff? There is a huge need for staff surge and just-in-time training of people who will suddenly become occ health deputies."

The pseudo-outbreak of pertussis also raised some potentially troubling issues about the employees' approach to working while sick or on furlough after an exposure. Dartmouth-Hitchcock was able to send sick employees home after a symptom screen. But he notes, "We found that some employees were sent home because we thought they shouldn't be in patient care environment were working in other health care environments."

The Department of Health and Human Services guidelines for community mitigation in pandemic influenza call for people to stay home if someone in their household is sick during a pandemic or if they have been exposed. What will that mean for health care workers?

"How are we going to retain employees in a setting of massive health care worker shortages, if we send them home but they're actually capable of working?" asks McLellan.

Pandemic plans will need to consider such issues, as well as child care, pet care and elder care, he says. Policies will need to address how and when to conduct symptom screening and to send sick employees home. For example, employee health and infection control professionals may decide to allow symptomatic health care workers who are taking antiviral medications to work with cohorted influenza patients.

What sickened the HCWs?

If it wasn't pertussis at Dartmouth-Hitchcock, what was it? "Most likely, this was a potpourri of different respiratory pathogens, most likely viral," says McLellan. Still, the symptoms were severe, he notes.

Dartmouth asked CDC to assist with the outbreak investigation and follow-up on the initial lab work. Of 134 suspect cases, 98 had been identified as pertussis by PCR and 36 by the classic case definition. When none of the cases resulted in a positive culture, Dartmouth asked for volunteers to have their blood drawn for serology testing. Of 39 serology cases, only one showed a moderate level of anti-pertussis antibodies.

CDC repeated PCR tests using two DNA targets and found only one positive, says Katrina Kretsinger, MD, CDC medical epidemiologist. "Pertussis may have been circulating, but we don't believe that pertussis was the etiology of most of this illness," she says. The episode points out the need to improve diagnostics for pertussis, she says.

Meanwhile, Dartmouth managed to control a respiratory disease outbreak that had severe symptoms. "It was definitely an outbreak, it just wasn't an outbreak of pertussis," she says. "It showed that isolation, work furlough and improved infection control processes can halt respiratory illness outbreak of diverse cause."

It underscored the effectiveness of basic infection control procedures. "CDC's 'ask-for-a-mask' respiratory hygiene and cough etiquette campaign is so appropriate for so many diseases," says Talbot.