Doctor and senior woman wearing facemasks during coronavirus and flu outbreak. Virus protection. COVID-2019..

Health officials have been drastically underestimating the number of nursing home residents and hospital patients infected with a so-called superbug, a new study suggests.

As many as 5%, or more than 30,000 residents and patients, may have the Methicillin-resistant Staphylococcus aureus (MRSA) at any given time, according to data recently released by the Association for Professionals in Infection Control and Epidemiology. That is eight to 11 times more common than other studies have found.

Researchers focused on cases in which the bacterium was merely present in a patient, not necessarily causing disease, as well. At least 46 out of every 1,000 patients were found to have the superbug, according a survey sent to more than 11,000 infection control professionals in more than 1,200 nursing homes and hospitals nationwide. They reported the number of patients in their facilities who were identified through test results as infected or colonized with MRSA on a given day between Oct. 1 and Nov. 10, 2006.

About 34 patients per 1,000 were infected with the superbug: They had skin or blood infections or some other clinical symptom. About 12 per 1,000 were colonized, having the bug but no illness, according to researchers.