Pertussis — commonly called whooping cough — is a highly contagious bacterial disease caused by Bordetella pertussis. In some countries, this disease is called the 100 days' cough or cough of 100 days. Symptoms are initially mild, and then develop into severe coughing fits, which produce the namesake high-pitched "whoop" sound in infected babies and children when they inhale air after coughing. The coughing stage lasts approximately six weeks before subsiding. Prevention by vaccination is of primary importance given the seriousness of the disease in children. Although treatment is of little direct benefit to the person infected, antibiotics are recommended because they shorten the duration of infectiousness.