AMDA Long Term Care Medicine 2012: Page 3 of 3

April 13, 2012

High Index of Suspicion for Norovirus Can Contain Potential Outbreaks

Prevention of norovirus outbreaks in long-term care (LTC) settings is difficult because of prodromal shedding and continued shedding after symptoms resolve. Knowing how to contain an outbreak is crucial because of the substantial morbidity and mortality it can cause, and the financial implications of an uncontrolled norovirus outbreak to a facility can be significant, said a panel of speakers at the AMDA Long Term Care Medicine 2012 meeting.

“Keep norovirus on top of your differential diagnosis,” advised Tae Joon Lee, MD, CMD, clinical assistant professor, department of family medicine, geriatric division, East Carolina University, Greenville, NC, whose facility had to temporarily ban admissions after a December 2008 outbreak.

Because norovirus is not a reportable illness in the United States, precise estimates of the incidence of outbreaks are not available; however, it is the leading cause of acute gastroenteritis in older nursing home residents. Although norovirus is more common in the winter, “it’s here year round,” warned David A. Nace, MD, MPH, CMD, director, LTC & Flu Programs, University of Pittsburgh, and chief of medical affairs, University of Pittsburgh Medical Center Senior Communities, PA.

Norovirus can be spread by person-to-person contact, excretions (feces, vomitus), contaminated surfaces, aerosolized particles, and contaminated food. In addition, because the norovirus genome undergoes frequent change, the ability for a person to maintain immunity is lost. “You can get it more than once,” said Nace.

Although the acute symptoms resolve within 3 to 4 days, the nonspecific symptoms (ie, lethargy) can last up to 19 days. Relapses between 3 and 8 days occur in 60% of patients.

A norovirus outbreak can be detected by applying the following four Kaplan criteria: mean or median illness duration of 12 to 60 hours; mean or median incubation period of 24 to 48 hours; vomiting in more than 50% of people; and no bacterial agent found. “When all four criteria are present, there’s a high likelihood that the outbreak is norovirus,” said Nace.

The difficulty in controlling norovirus outbreaks in healthcare settings is attributable to several factors, including a low infectious dose of the virus; environmental stability of the virus; a large human reservoir of infection; ability of the virus to be transferred by a variety of routes; substantial strain diversity; and prodromal viral shedding, which occurs at least 24 hours before symptoms manifest and continues after symptoms resolve, noted Nace, whose facility had a 6-week shutdown after failure to control an outbreak.

An outbreak can cause “lots of chaos in the facility,” said Lee. Dining rooms and other gathering areas may need to be temporarily closed, some patients may need to be quarantined, a substantial proportion of staff will miss work while others will need to work overtime, and temporary workers not familiar with the facility may need to be called in, he noted. An outbreak of 24 cases at his facility resulted in a median of 2.5 days of missed work, required a ban on new admissions, and restricted visitation. Ill staff were quarantined at home until 48 hours after their gastrointestinal symptoms resolved. The outbreak cost the facility $34,000 from the ban on admissions and additional staffing and patient care expenses. Factoring in emergency department visits and hospitalizations, the total cost to the system was estimated to be $49,000.

In 2011, the Centers for Disease Control and Prevention (CDC) issued healthcare facility guidelines that contain recommendations on preventing and containing norovirus outbreaks in healthcare settings. Because most household disinfectants have little or no activity against norovirus, preventing outbreaks is a challenge, said Taranisia MacCannell, PhD, MSc, epidemiologist, Division of Healthcare Quality Promotion, CDC. The evidence for hand hygiene in preventing transmission is inconclusive, but the CDC recommends soap and water after having contact with patients and use of an ethanol-based hand sanitizer before contact with patients who have norovirus.

If a resident has symptoms consistent with norovirus gastroenteritis, the CDC recommends placing him or her on contact precautions in a single-occupancy room (evidence: category 1B). Specimens for norovirus should be taken during the acute phase of the patient’s illness, or 3 or more days after onset, said MacCannell.

The full CDC guidelines can be found at

—Wayne Kuznar