More Americans have asthma than ever before. That doctors aren't sure what's causing the spike.
Researchers with the Centers for Disease Control say the number of people diagnosed with asthma grew by 4.3 million between 2001 and 2009.
Nearly one in 12 Americans have asthma.
Doctors are puzzled by the numbers - as states have enacted smoking bans, the risk of getting asthma from secondhand smoke has decreased.
The costs to treat asthma are up too - estimated at $56 billion.