TUALATIN, Ore. (AP) – District officials say three Tualatin High School students were recently diagnosed with whooping cough.

Those cases add to one at Northeast Portland’s Grant High School, where a student was diagnosed with the illness earlier this week.

Washington County has seen 36 confirmed or suspected cases of the illness so far this year, county health department spokeswoman Wendy Gordon told The Oregonian/OregonLive.

Whooping cough, or pertussis, causes severe, violent coughing and spreads easily in groups.

Other signs include cold-like symptoms like a runny nose but usually no fever.

There is a vaccine for pertussis, but the health department said it wears off over time.