A suburban Philadelphia high school is dealing with its second whooping cough case of the academic year.

Wissahickon High School sent a letter to parents Friday saying a sophomore had been diagnosed with the respiratory disease and that other students may have been exposed.

Montgomery County health officials confirmed the district's first whooping cough case Sept. 11.

The disease known as pertussis is highly contagious in people who haven't been vaccinated. It's generally not helped by cough syrups or other common remedies.

Health department and school officials say in the letter that the illness can be very severe, though it is rarely fatal — mostly for infants.

Pennsylvania requires students be vaccinated for whooping cough before they enter the seventh grade. Exemptions are made for medical, religious and other objections.