The number of whooping cough cases in North Dakota dropped for the third straight year in 2007.

Thirteen cases of whooping cough, or pertussis, were reported in the state last year, compared with 41 in 2006 and 165 in 2005, the Health Department said.

In 2004, North Dakota had a record 757 whooping cough cases.

A newer vaccine that became available in 2005 for adolescents and adults has helped slow the spread of whooping cough, said Molly Sander, immunization surveillance coordinator with the Health Department.

A vaccine shot for tetanus, diphtheria and pertussis will be required for students entering middle school in North Dakota this fall, she said.

- Associated Press