The seroepidemiological investigation for COVID-19 virus infection is intended to provide key epidemiological and serologic characteristics of COVID-19 virus. The study will be provided as a longitudinal cohort study with serial sampling of the same individuals at minimum two different time-points separated by at least 21 days. The first time-point will be as quickly as possible, and the second time-point will be after 3 weeks. It will also be possible to test the individuals at later time-points if resources are available. The following is based on the WHO standardized protocol “Population-based age-stratified seroepidemiological investigation protocol for COVID-19 virus infection” and has been redesigned to investigate the extent of infection, as determined by virus- and/or seropositivity, among an asymptomatic population of healthcare workers in an orthopaedic department in Oslo, Norway at early phase in the epidemic COVID-19 virus infection. As well as to follow-up the healthcare workers and determine the rate of infection during the phases of the epidemy.