A health board has written to seven people who were in a hospital around the same time a patient was infected with hepatitis C.
NHS Lanarkshire said it took the measure as a precaution after an inquiry concluded the patient caught the virus during an inpatient stay at Monklands Hospital in Airdrie, North Lanarkshire.
The seven people contacted were all in the hospital around the same time in April 2012.
Exactly how the virus was transmitted remains uncertain but it is "very unlikely" that any of the seven had been infected, the health board said.
Dr Iain Wallace, NHS Lanarkshire medical director, said: "We are committed to providing the highest standards of infection control across all of our services.
"It is of the greatest regret that on this occasion we did not do so.
"We have already used the lessons learned from this case to make further improvements to our infection control processes and practice."
Dr John Logan, consultant in public medicine, said: "We have carried out a detailed and thorough investigation.
"While it is very unlikely that anyone else has been infected in connection with this, we have taken the precaution of providing seven patients with information about the situation and a questions and answers document.
"They have also been offered an appointment to see a hepatitis C specialist for further information and advice and to have a test for hepatitis C should they wish to be tested."
Improvements have been made to infection control on the hospital's wards as a result of the investigation, the health board said.