Four students at Rogers High School in Puyallup have been diagnosed with whooping cough, according to the Puyallup School District.

The district said on Tuesday it is working with Pierce County Public Health.

The district has contacted the families of students who were most at risk of exposure from infected students, according to a letter sent to families.

In the letter, the district encouraged parents to make sure their child’s pertussis vaccination was up to date or to get vaccinated if they have not done so yet.

Whooping cough is spread when an infected person coughs, sneezes, or talks.

It starts as a cold with a runny nose and turns into a cough, which can last several weeks. Coughing can come in fits or can lead to vomiting.