Almost a dozen more whooping cough cases have been reported since Friday,

Island County Medical Officer Roger Case said Monday.

“We are now at 42 and expect more,” Case said.

A total of 31 cases of the disease, called pertussis, were reported through July 11.

The disease — a highly contagious bacterial infection — is spread through respiratory droplets when an infected person coughs, sneezes or talks. The greatest risk of spread is during the early stage when it appears to be a cold.

Case said earlier that the Island County Public Health Department has laboratory-confirmed cases of whooping cough that came when people attended the recent swimming classes held at Admiral’s Cove Pool between June 23 through July 2.

The health department is looking for anyone who attended classes that were held at 9:40, 11, 11:40 a.m. and 12:20 p.m.

All cases of pertussis should be reported to the health department at 360-679-7350.