"Do shorter visiting times reduce infection spread?"

The visiting times of a local hospital where my relative is an inpatient have been reduced to 2-3 and 7-8 pm (2 hrs a day) to reduce the spread of norovirus and other infections from visitors to patients.

The five nearest similar hospitals/trusts have afternoon visiting times of 3hrs (1 trust), 3.5 hrs (2 trusts), 5.5 hrs (one trust) and 6hrs (one trust).

All the six trusts have the same NHS League Table rating (mid-range) for incidence of drug resistant bacterial infections (there's no rating for norovirus).

Assuming the risk of passing on the virus is roughly the same in each of these trusts and they are roughly equal in coping with spread of infection, why are visiting hours so different?

Visitors, especially near relatives, are important to patients, so if visiting time needs to be restricted for patient safety, then all the six trusts should have the same visiting hours based on some scientific research which shows the hours selected do actually reduce norovirus, rather than what currently appears to be a figure chosen out of a hat.