For analysis of clinical parameters, all identified PIAH patients with symptoms starting before hospitalization or less than 72 h after hospitalization were included. Nosocomial infections with symptoms starting >72 h after hospitalization (n = 10 cases, including one fatality) were excluded from the present analysis and will be described elsewhere. Data were analyzed descriptively using SPSS (version 18.0 and 19.0, Chicago, IL). Continuous data were reported as median with interquartile range (IQR) and categorical variables as percentage of patients.