In the treatment, care and isolation of COVID-19 patients, one of the most important issues is determining the duration of infectiousness. The current Dutch guideline advises at least 14 days of isolation for seriously ill patients, which is the case for most admitted patients, and at least 21 days for intubated patients. It is believed that in most cases this isolation duration is too long, which is highly undesirable for patients staying in closed single-occupancy rooms. This is known to result in limited contact with healthcare workers (HCW) and to be associated with a higher level of depression among patients. The longer the isolation, the higher the workload for HCW and the higher the costs (e.g. with about 0.5 million admission days in the Netherlands, these work out at about €14 million on personal protective equipment [PPE] and cleaning alone). Additionally, isolation demands a larger healthcare workforce, yielding less capacity to provide other care to non-COVID-19 patients, with numerous other consequences. On the other hand, it is possible that some patients were discontinued from isolation too early, leading to a risk of transmission to other patients and to HCW. In conclusion, duration of isolation should be as short as possible for proper patient flow and to avoid unnecessary burden to patients and HCW, and thus to healthcare in general. Therefore, there is an urgent need to define the period of infectiousness of COVID-19. We will develop a safe and effective algorithm for decision on timely discontinuation of isolation of COVID-19 hospitalized patients.