(CNN) – For the second year in a row, the US has surpassed 25,000 whooping cough cases — another sign of the risks of falling vaccination levels.

Often called the “100-day cough,” whooping cough or pertussis begins with cold-like symptoms such as runny nose, fever or cough that can progress to coughing fits that last weeks or months, according to the US Centers for Disease Control and Prevention. A “whoop” sound when coughing may appear in the second phase of illness. (Read More)