Up to two million people in Scotland may have been infected with swine flu during the outbreak of winter 2009-2010, making the flu much more widespread than previously thought, according to a study published by researchers from the University of Edinburgh in PLoS One, BBC News reports (6/8).

Researchers took blood samples from 1,600 Scottish adults and tested for antibodies to the H1N1 flu strain. “Most of the 44 percent who tested positive had contracted swine flu, although some had acquired immunity from a previous bout of flu, or had been vaccinated,” according to a University of Edinburgh press release (6/8). The researchers believe that of the nearly two million people who may have had swine flu, only about 100,000 consulted a physician, the Daily Record notes (O’Neil, 6/9).