Respiratory tract outbreak modeling with case definition criteria: A proposal for a standardized clinical approach in nursing homes.

ABSTRACT

OBJECTIVES: This study aimed to monitor respiratory tract outbreaks in nursing homes (NH) by applying standardized case definition criteria, pathogen identification and estimated mortality impact. PATIENTS AND METHODS: This longitudinal, observational study described NH outbreaks with temperature (T°), upper respiratory sign, lower respiratory sign (LRS), general status deterioration, general signs, and mortality. Viral examinations allowed for analysis of developing outbreaks based on positive, negative, or no tests (Flu+/Flu-/NT-Flu). RESULTS: Forty-six influenza identification episodes (Flu+, 1067 patients), 14 Flu- (409 patients), and 18 NT-Flu (381 patients) were analyzed. Viral examinations were conducted mainly among residents with T° (84.8% [302/356]). A specific temperature pattern was observed in Flu+ outbreaks 35.1% of infected residents with T° without LRS, 15.6% in Flu- episodes, and 17.1% vs. 29.1% in LRS without T°. A median temperature (MT) of ≥38.3 °C was observed in Flu+ outbreaks. MT analysis of the 18 NT-Flu episodes identified five outbreaks with high temperatures (MT ≥38.2 °C) and high mortality. Conversely, the 13 NT-Flu outbreaks with lower MT (<38.0 °C) were associated with lower total mortality. Similar clinical pictures led to closely comparable all-cause mortality impacts, particularly in Flu+, Flu-, and NT-Flu with MT of ≥38.2 °C. CONCLUSIONS: Validated sign/symptom monitoring highlighted some specificities of respiratory NH outbreaks and could be a complementary approach, taking into account common and atypical clinical pictures, assessing mortality and initiating virological investigations and infection control measures.