The number of suspected cases of whooping cough on Whidbey Island has risen to 59, county health officials said Monday.

Of the current 50 confirmed cases of whooping cough in Island County, 21 were reported on South Whidbey, 22 came from the Coupeville area and seven in Oak Harbor.

Nine other cases are considered likely but haven’t been confirmed.

Also known as pertussis, whooping cough is a highly contagious bacterial infection that causes coughing and gagging with little or no fever. An infected person may have coughing episodes that may end in vomiting or cause a “whoop” sound when the person tries to breathe in. Children under age 1 are the most vulnerable to the ravages of this disease which causes the death of over 300,000 children worldwide each year.

The pertussis rate in Island County per 1,000 people is 136.8 in South Whidbey, 229.4 in Coupeville and 18.2 in Oak Harbor.

Island County Chief Medical Officer Roger Case plans to issue a detailed report as to exactly how many among these 59 cases were fully immunized, partially immunized or had no immunization for pertussis.