Keith Haglund is managing editor of Caring for the Ages.
An investigation of a string of norovirus outbreaks in one long-term care facility has yielded insights into how the gastroenteritis virus might spread in an institution, as well as how infection-control lapses might compound such viral outbreaks.
In late 2007, the Oregon Public Health Division learned of the third acute gastroenteritis outbreak within a year at a 690-resident facility in the state. Investigators from the Oregon division as well as the Centers for Disease Control and Prevention descended on the unnamed facility while the outbreak was still underway and logged extensive data on both residents and employees.
By genotyping current and stored norovirus samples from all three outbreaks, the researchers learned, “Each of the three outbreaks … was caused by different norovirus variants,” suggesting repeated introduction of virus, the team wrote in the Morbidity and Mortality Weekly Report (2009;58:694–8).
Because of the residents' long tenure at the facility and their lack of mobility, the researchers concluded that “employees or visitors were more likely to have contributed to the introduction of new infection and dissemination across wards.”
Two other indicators that staff members introduced infection were that only 16 of the 22 wards in the facility were hit by the outbreak and those wards were administered by different staff than those in the 6 unaffected wards.
The same ward-to-ward differences led the researchers to conclude that the virus was spread between people and was not from a food source. “Although all wards were served by a common food supply, prolonged transmission occurred only within certain wards,” wrote the team.
The 242 employees in wards with 10 or more cases during the third outbreak were asked to complete anonymous questionnaires about such actions as using gloves, washing their hands, wearing masks, and cleaning up after sick residents. The team also analyzed stool samples from 25 ill residents and employees and environmental swab samples from the wards hardest hit by norovirus.
Employees were at much higher risks of infection if they hadn't worked at the facility long and if they had cleaned up vomitus at work. Each of these parameters carried a 1.6 adjusted relative risk. The researchers said they couldn't explain the difference made by length of employment but noted that other research has implicated aerosolized vomitus as a norovirus vector.
“Gloves were worn by 97% of surveyed employees who cleaned vomitus, but they rarely wore gowns or aprons and masks while cleaning vomitus,” the researchers found.
The Oregon/CDC team recommended the following ways to reduce the spread of infection when an ill person has vomited or defecated:
▸ Limit aerosolization during clean-up by minimal agitation of vomitus or feces while using disposable towels and impervious waste bags.
▸ Thoroughly clean and disinfect surfaces with freshly made 5,000-ppm hypochlorite solution or other product registered by the Environmental Protection Agency.
▸ Wear gloves, masks, and gowns when cleaning up these materials.
The team reported several “major barriers or lapses in infection control” at the facility. First, having overall staffing shortages and policies that discouraged sick leave meant that many of the 35% of employees who were sick with norovirus on the hard-hit wards failed to stay home.
Second, a particular shortage of housekeeping staff and the absence of any EPA-registered disinfectants meant residents' rooms weren't cleaned properly. Third, the team found an insufficient number of hand-washing stations, with none in dining areas or residents' rooms.
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