Getting a Handle on Swine Flu

When it comes to swine flu, we're not getting the full story.

The number of swine flu infections, hospitalizations, and deaths in the U.S. were significantly underreported earlier this year, government estimates show.

There were just under 44,000 lab-confirmed cases of H1N1 virus reported across the country through July 23 of this year, but the true number may have been as high as 5.7 million, researchers at the Centers for Disease Control and Prevention and Harvard School of Public Health found.

Official figures found a little more than 5,000 hospitalizations and 300 deaths from the first wave of the flu. But those numbers probably were underestimated as well, the researchers say. Hospitalizations may have been four times as high. There may have been as many as 800 deaths, though researchers say they're developing a more sophisticated model to determine how many people died.

The new study shows how difficult it is to predict numbers in a pandemic. The flu threatens to crowd hospital emergency rooms and intensive care units and is putting stress on public health systems. Insurers are reporting higher costs due to larger-than-expected medical claims and employers are bracing for higher rates of sick workers.

The reason the count is so low is because not everyone gets tested for the virus. Lab results also can be inconclusive depending on timing and quality of testing.

"Unfortunately, relying on laboratory-confirmed cases limits the ability to understand the full impact and severity of the epidemic, especially when severe cases are more likely to be recognized," the researchers said.