The New York City Health Department says that hundreds of thousands of city residents may have contracted swine flu.

Roughly 6.9 percent of the 1,006 residents surveyed by the Health Department from May 20 to 27 reported experiencing flu-like symptoms in April and May. That suggests more than 570,000 New Yorkers may have fallen ill.

Limited testing means that only a fraction of possible cases have been confirmed. New York City Health Commissioner Thomas Farley says the study suggests that only a small portion of the hundreds of thousands of possible cases "developed severe disease." Tests have confirmed 820 cases in the city.

The Health Department on Wednesday also reported three more deaths from swine flu, bringing the city's total to 12. The city said that one victim was 30 to 39 years old, another was 50 to 59 and another was over 65.