Scientists with the Centers for Disease Control and Prevention say asthma is the most common underlying condition associated with severe cases of H1N1.
The CDC performed an analysis in 10 states of people hospitalized with H1N1.
In children, other much rarer chronic conditions, such as sickle cell anemia, cerebral palsy and muscular dystrophy, are also predisposing patients to life-threatening bouts of the virus, federal health officials said.
This doesn't mean that having these conditions make a person more likely to contract H1N1. It means that once a person has the virus, these conditions make it much more serious.
The CDC studied the experience of about 1,400 people older than 18, and 500 children, who had been hospitalized in California, Colorado, Connecticut, Georgia, Maryland, Minnesota, New Mexico, New York, Oregon and Tennessee.
Among the hospitalized adults, 26 percent had asthma; 10 percent had diabetes; 8 percent had a chronic lung disease such as emphysema; 7.6 percent were immunosuppressed from cancer, HIV infection or other ailment; and 6.1 percent were pregnant. (Heart disease was also common, although CDC officials couldn't immediately say what fraction of patients had it.)
