Health officials say 2012 was the nation's worst year for whooping cough in nearly six decades.
Almost 42,000 cases were reported last year, the most since 1955.
Those are preliminary numbers as The Centers for Disease Control and Prevention as the agency is still gathering information, and says the number could climb to 50,000 cases.
Whooping cough tends to run in multi-year cycles, and experts say last year appears to have been a peak. Also, a newer version of the whooping cough vaccine doesn't last as long as experts predicted.
There is some good news: There were only eighteen deaths from the disease last year.
Faster diagnosis and treating the disease during outbreaks kept those numbers low, according to experts.
Thousands of people dies from whopping cough before a vaccine was developed in the 1940's.