There is no fixed period. There appears to be a range of answers to this question. Recently, it has been found that coronavirus strains that affect humans can remain active on hard surfaces from 2 or 3 hours to 9 days. Most appear to last for 2-4 days. That is why it is important to clean such surfaces regularly. Although not a hard surface, coronavirus can remain alive on or in your mattress for up to 2 days. Much depends on how often people touch or rub on the surface and of the ambient temperature.