London: The swine flu outbreak during the winter of 2009-2010 was much more widespread than previously realized, a study says.
Blood samples taken from Scottish adults in March last year at the end of the H1N1 flu season showed that almost half were carrying antibodies to the virus. Antibodies are either produced by the body or injected through vaccines when the body is exposed to pathogens.
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, the journal Public Library of Science reports.
Professor Mark Woolhouse of the Edinburgh`s Centre for Infectious Diseases, who led the study, said: "This flu spread very quickly. Fortunately most cases were mild but this also means that they weren`t reported."
"Testing for antibodies to flu could be invaluable in tracking future pandemics and targeting vaccination to those groups who most need it," he added, according to an Edinburgh statement.
The research shows that many cases of swine flu went unreported. Only 100,000 people consulted their doctor regarding flu, out of about two million who are believed to have contracted the virus.
People living in the most deprived areas were twice as likely to have contracted the virus. Scientists add that it is possible that many people who were vaccinated against the virus were already immune.
Almost 1,600 adults from the east of Scotland and Glasgow, who are participants in the Generation Scotland Scottish Family Health Study voluntary health scheme, took part in the study.