Washington: Up to 5.7 million people in the United States may have been infected with swine flu in the first four months of the outbreak, or more than 100 times the number of laboratory-confirmed cases that were reported, a study has said.
Using a multiplier model, researchers from the Centres for Disease Control and Prevention demonstrated that "the reported cases of laboratory confirmed pandemic (H1N1) 2009 are likely a substantial underestimation of the total number of actual illnesses that occurred in the community during the spring of 2009," lead author Carrie Reed wrote in the study.
The researchers estimated that between 1.8 million to 5.7 million cases of H1N1 flu occurred in the United States in the four months from April, when the virus was first reported.
Of those cases, between 9,000 and 21,000 were hospitalised, the report estimated.
Although the report did not estimate the number of deaths from swine flu, Read pointed out that the ratio of deaths to hospitalisations in the four months to July 23 was six per cent. That would mean that around 1,200 people died of H1N1 flu in the United States in the first months of the outbreak.
The official US death rate from swine flu at the end of July was less than 300.
Bureau Report