Fluid buildup a danger from flu.

• Position: Respiratory System

In a fight against respiratory infections, the body typically produces a little fluid to help the lungs generate a productive cough. However, research from the University of North Carolina, Chapel Hill, shows that the influenza virus can tip the balance toward too much fluid in the lungs, interfering with the supply of oxygen to the rest of the body.

An immune response ultimately is needed to eliminate the virus, but this research suggests that it is not the presence of the virus alone that does all the harm to a sick person. Instead, the fluid buildup deep inside the lungs might help kill a person infected with the flu. "When people die of these ill nesses, they're dying because they can't breathe," the study states. "If the lungs aren't working well, then it does not matter whether a week from now you can make an immune response and clear the virus if you can't survive that long because you can't get oxygen."

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Detailing exactly how flu interferes with fluid clearance in the lungs lays the groundwork for a second phase of related studies to test a new therapy--a drug that already is known to regulate the amount of fluid that builds up in infected lungs. In the event of a flu...