SANFORD, Maine (AP)   Maine school officials say six students in Sanford have been diagnosed with whooping cough.

WMTW-TV reports there were four reported cases at Margaret Chase Smith School and two cases at Sanford Junior High School. Parents have been notified.

Whooping cough, or pertussis, is spread through sneezing or coughing. Symptoms include sore throat, uncontrollable coughing and fever.

The Maine Centers for Disease Control says the state has one of the highest rates of pertussis in the country. Incoming seventh-grade public school students are required to receive a second dose of Tdap, a vaccine that protects against tetanus, pertussis and diphtheria.

Efforts have been hindered by parents who opt out of vaccination. However, officials believe stricter standards will help the general population.