A case of whooping cough has been confirmed at Saanich's Mount Douglas Secondary School.

Island Health sent a letter to parents after a person at the school contracted the highly contagious respiratory infection, also known as pertussis.

It did not say whether the person who caught pertussis was a student, teacher or support staff member.

"Individuals who have attended the school may have been in contact with the bacteria, which are spread by coughing," the health authority said.

Infections usually begin with cold-like symptoms that may progress to the distinct-sounding cough as well as gagging or vomiting, which can last for several weeks.

Island Health says infants and pregnant mothers in their third trimester are particularly at risk. One infant out of every 170 who gets pertussis will die, according to the BC Centre for Disease Control.

Island Health is also urging parents to make sure their kids are up-to-date with immunizations against whooping cough.

The BCCDC's latest pertussis numbers in B.C. show that 641 people were infected in 2017, with 209 of those infections happening on Vancouver Island.