Grounds for variation in HCWs' perceptions on the appropriateness to ask to report symptoms seem to be cultural, with participants in Germany holding stronger views on the need to protect privacy and confidentiality. Any concepts developed for surveillance in this population will need to be sufficiently flexible to embrace a wide range of attitudes and practices. An example to circumvent barriers potentially predominantly in Germany may be to use aggregate data without identifiers and information on reasons for absence to highlight patterns. This concept has been explored in further detail in the REACT surveillance system framework model report [12] .