Types of infectious outbreaks and their impact in elderly care facilities: a review of the literature.

BACKGROUND infectious outbreaks in long-term care facilities (LTCFs) tend to have a significant impact on infection rates and mortality rates of the residents. OBJECTIVES this review aimed to update the information on pathogens identified in such outbreaks and to try to explore indicators that reflect the impact of outbreaks among residents and health care workers (HCWs). METHODS MEDLINE (1966-2008) was used to identify outbreaks using the following thesaurus terms: 'Cross-Infection', 'Disease Outbreaks', 'Urinary-Tract Infections' and 'Blood-Borne Pathogens'. Elderly care facilities were identified with the following thesaurus terms: 'Long-Term Care', 'Assisted-Living Facilities', 'Homes for the Aged' and 'Nursing Homes'. Age category was limited using 'Aged'. RESULTS thirty-seven pathogens were associated with 206 outbreaks. The largest number of reported outbreaks by a single pathogen involved the influenza virus, followed by noroviruses. Among residents, the highest median attack rate for respiratory infection outbreaks was caused by Chlamydia pneumoniae (46%), followed by respiratory syncytial virus (40%). In gastrointestinal tract infection outbreaks, high median attack rates were caused by Clostridium perfringens (48%) and noroviruses (45%). Outbreaks with high median case fatality rates were caused by Group A Streptococci (50%) and Streptococcus pneumoniae (44%). High median attack rates for HCWs were caused by C. pneumoniae (41%), noroviruses (42%) and scabies (36%). CONCLUSION a variety of infectious agents were identified as the cause of outbreaks in the elderly and HCWs in LTCFs. Attack rates and case fatality rates are useful indicators for setting priorities for education and prevention of the outbreaks.