Experience of new coronaviruses (SARS-CoV and MERS-CoV) has been used to inform this guidance. The risk of infection depends on many factors, including:
- the type of surfaces contaminated
- the amount of virus shed from the individual
- the time the individual spent in the setting
- the time since the individual was last in the setting
The infection risk from coronavirus (COVID-19) following contamination of the environment decreases over time. It is not yet clear at what point there is no risk. However, studies of other viruses in the same family suggest that, in most circumstances, the risk is likely to be reduced significantly after 72 hours.