Twin Peaks: A Persistent Norovirus Outbreak
Raises questions about spread from asymptomatic patients
A nasty, easily transmitted bug
that has ruined many a cruise vacation, norovirus can cause chaotic, labor-intensive outbreaks in hospitals. In that regard, an infection preventionists recently described a norovirus outbreak that kept reigniting in different locations in a situation somewhat akin to fighting a forest fire in high wind.
How bad was it? When traditional and enhanced measures had been exhausted, the hospital shut down the affected rehab unit for deep cleaning and disinfection by a special cleaning outfit, an IP said recently in Portland at the annual conference of the Association for Professionals in Infection Control and Epidemiology.
“This outbreak had a tremendous impact on our facility,” said Deborah Danzig Brodie, MPH, BSN, CIC, an infection preventionist at Hebrew SeniorLife in Roslindale, MA. “It had a tremendous impact on the patients, the families and the staff — and on our financial budget, as you can imagine. During the second peak of the outbreak, we were closed to admissions. We hired a cleaning company from New York City; they came in with hazmat suits. We moved patients to one side of the unit, and they disinfected the entire [other] side. Once we knew that the place was completely disinfected — you could eat off the floor — we finally reopened to admissions. Thank God, because it was six weeks later.”
Index Case
The outbreak began innocently enough when a paitent from an acute care hospital was admitted to the short-term rehab unit at SeniorLife. The rehab unit has some 50 beds and is divided into north and south units. There are only two private rooms and four private rooms with a shared bath. The rest are double rooms with a shared bath.
“You can imagine our challenge for room placement,” she said. “Our first case started with a new admission from an acute care facility on January 3, 2016 with GI symptoms. We weren’t that concerned — the patient went on contact-plus precautions, we initiated CDC recommendations per protocol.”
Over the next month, the total norovirus cases in the unit would go from one to 31. The index case and one other came in from the community; the rest were apparently acquired due to cross-transmission in the rehab unit.1
As IPs are aware, norovirus can occur year-round, but has increased prevalence during the late fall and winter months. The most common cause of gastroenteritis, norovirus is extremely contagious and can be transmitted by food, water, environmental surfaces, and directly from person to person.
“The incubation period is usually from 12 to 48 hours post-exposure to the virus,” Brodie said. “It usually lasts about one to three days, but may last longer — especially in the elderly and in hospitalized patients. It’s transmitted most frequently from symptomatic patients via the fecal-oral route, respiratory droplets — especially if somebody vomits. The virus can spread through the aerosolized particles.”
The note about usual transmission by symptomatic patients is significant, as the “second peak” of the outbreak was started by a patient who was asymptomatic for four days and was no longer considered infectious by traditional standards.
But, at the beginning, the index case was admitted. “Then, we had a new case a few days later, followed by a new admission,” Brodie says. “We still weren’t that concerned. However, three days later we had four cases in one day. That’s when we became really concerned, and that was followed by several other cases.”
The department of health was contacted and Brodie and her colleagues doubled down on infection control measures to quell the outbreak.
“We were observant,” she said. “We were vigilant with our infection control, but all of a sudden we had a whole new crop [of cases].”
The outbreak had two peaks, as cases from the north side of the unit eventually spread to the south side via the aforementioned asymptomatic patient, “RH.” He became symptomatic on Jan. 13, apparently acquiring it from his roommate, who had become symptomatic two days earlier.
“RH was ready to come off precautions; his roommate was not ready yet,” she said. “It had been five days — and, by the way, RH was only symptomatic for one day.”
Brodie and colleagues consulted with health department officials, who gave the green light to take RH off precautions. He was moved to a south side unit to a room with another asymptomatic patient. About 2.5 days later, RH’s new roommate had symptomatic infection with norovirus.
Continuing Problems
“We were shocked — what was happening here?” Brodie said. “In a matter of a few days, we had another cluster — a norovirus outbreak even worse than the first time.”
They sent stool samples to the state and went back to the medical literature, finding two significant pieces of information.
“We realized that transmission may still occur once acute symptoms have resolved,” she said. “The usual pattern is you can discontinue precautions if they’re asymptomatic for 72 hours.” In this case, RH was asymptomatic for four days, but they obviously were not dealing with a normal outbreak — and, perhaps, not a normal norovirus. The mean viral load in the stool samples was much higher than historical levels.
“We realized also that norovirus shedding can occur in the stool for at least three weeks,” she said. “Even though the person is most infectious during the symptomatic period. Our experience suggests the transmission can occur in asymptomatic patients. We realized our traditional interventions weren’t working. We had to up the ante with infection control practice.”
The multiple overlapping efforts included posting hand hygiene signs in all areas, adding hand hygiene stations in the unit, increasing environmental cleaning, and washing the hands of all patients with soap and water before meals.
In addition, confirmed or suspected norovirus patients were placed under enhanced contact-plus and droplet isolation precautions.
“That meant anybody crossing the threshold had to wash hands with soap and water,” she said. “That was everybody — and I have to say they were really compliant with that. We enhanced their housekeeping activities to include all high-touch areas and on different shifts, on both units, common areas, and the kitchen.”
A decision was made for ill patients who became asymptomatic to remain in isolation for an increased period, which quickly became until they were discharged as the hospital stepped up measures rapidly as cases continued.
“You have to understand, our average length of stay is two weeks,” she said. “If they have a medical complication, they may be there for three weeks. That’s a long time to be on precautions.”
Given this situation, an extra effort was made to stay in communication with isolated patients, family, and staff caring for them. As noted, the outbreak was finally stopped with closure of the unit to new admissions and extensive disinfection of the entire area.
REFERENCE
- Brodie DD, Kandel, R. Lessons Learned: A Journey Through a Norovirus Outbreak. Oral Abstract 1207. APIC 44th Annual Educational Conference. Portland, OR: June 14-16.
A nasty, easily transmitted bug
that has ruined many a cruise vacation, norovirus can cause chaotic, labor-intensive outbreaks in hospitals. In that regard, an infection preventionists recently described a norovirus outbreak that kept reigniting in different locations in a situation somewhat akin to fighting a forest fire in high wind.
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