But Dr Smith added that hospital-acquired or “nosocomial” infections have reduced in recent months, with the rate of infection “very, very small” compared to the huge number of interactions in health and care settings across the country every day.
Patients admitted to hospitals are tested for Covid-19 on admission, or if they develop symptoms, but not routinely on discharge, Health Secretary Jeane Freeman said.
Dr Smith told the coronavirus daily briefing on Wednesday: "It's one of the areas where there's still quite significant mixing between people from different places just now.
"I don’t think it would surprise you that it’s one of the areas that features most strongly in the analysis of of where people have been when they have tested positive.
"That doesn’t mean to say that’s where they caught it, it just means they’ve been in that environment.”
Dr Smith added: "Nonetheless, there’s an association there, and it is still evident that health and social care places or interactions is still an area where there is some degree of risk of infection at this moment in time.
"We have to make sure that’s understood as proportionate, given the volume of interactions that there still are across the country on a day to day basis in that setting, actually the proportion of people who test positive after such an interaction is very, very small.”
Ms Freeman said the latest data shows an improvement in the number of Covid-19 cases thought to be associated with hospital infection.
She added that there is no routine policy for testing patients on discharge from hospital.
“We don't have a standard policy of testing everyone – remember people will have been tested when they came into hospital,” she said on Wednesday.
"Obviously if they have acquired Covid or shown signs of Covid during their hospital stay they will have been tested for that, and they won't be discharged until they are negative, but other than that there is no policy as a standard of testing individuals before they are discharged, although clinicians are always the right people to make those decisions if they think that that's appropriate.”