An Outbreak of Norovirus Infection on a Long-Term-Care Facility in Brazil

Background: Noroviruses, formerly referred to as “Norwalk-like viruses”, are important pathogens in hospitals and long-term-care facilities outbreaks. Among Long-Term-Care Facility residents, fecal incontinence, dementia, and immobility are common conditions that may facilitate extensive contamination of the environment with the fecal pathogens.

Objective: To describe the characteristics of a norovirus outbreak on a Long-Term-Care Facility in Brazil using epidemiologic and molecular diagnostic methods, and evaluate the measures of control and prevention.

Methods: A survey study of a norovirus outbreak occurred from June 21 to August 17, 2009. Epidemiological and clinical characteristics of the norovirus infections were described by chart review. For the purpose of this study, an outbreak was defined as three or more related cases with acute onset of diarrhea (two or more episodes in 24 hours). The Kaplan criteria was used for the diagnosis of presumptive norovirus infection, including stool cultures negatives for bacterial pathogens, vomiting in more than 50% of cases, an incubation period of 24-48 hours, and a mean or median illness duration of 12 – 72 hours. These samples were assayed for the presence of norovirus using the kit RIDASCREEN® Norovirus (R-Biopharm AG, Darmstadt, Germany) following the manufacture’s instructions, and reverse transcription-polymerase chain reaction (RT-PCR).  The nucleotide sequence of PCR (cDNA) products for norovirus was determined with the Big-Dye terminator cycle sequencing kit and an automated ABI Prism 377 (PE Applied Biosystems, Inc, USA).

Results: Attack rates among residents were 43.2% and 7.7% among employees. The main clinical feature was diarrhea, which affected 100% of residents and employees. Eighty percent of specimens were positive by RIDASCREEN® Norovirus analyses, and identified as norovirus genogroup GII by RT-PCR. Sixteen seven percent of residents were women and their ages ranged from 70 to 103 years. Residents had a median of two comorbid conditions, 79.4% with cardiovascular or chronic pulmonary condition, 21.9% with diabetes, 52% with dementia and 36.9% with any gastrointestinal disorder. There was not death in this outbreak. Within 48 to 72 hours after the symptoms of diarrhea in residents and employees, the principal infection control strategies were instituted including staff education, reinforcement of hand hygiene, implementation of contact precautions until resident has been asymptomatic for 48-72 hours, use of mask when assisting vomiting residents or cleaning soiled fomites, terminal cleaning of the rooms in Long-Term-Care Facility and exclusion of symptomatic employees from work until 48-72 hours after the resolution of their symptoms. Conclusions: The early infection-control measures associated in surveillance is required to keep our long-term care facilities free of noroviruses and protect those who are most vulnerable.