EXETER � The spell of whooping cough at Exeter High School has reached an �outbreak� level, according to the New Hampshire Department of Health and Human Services.

Jake Leon, director of communication for New Hampshire DHHS, confirmed Monday there are currently 22 diagnosed cases of pertussis, commonly known as whooping cough, associated with Exeter High School.

�This is considered an outbreak because there are more cases than what would normally be observed. New Hampshire typically sees 50 to 150 pertussis cases per year,� Leon said. �DHHS continues to investigate possible cases and instructs people with pertussis cases to take a 5-day course of antibiotics and to stay home or otherwise avoid communal settings for the 5-day duration to prevent further exposure.�

Associate Superintendent Esther Asbell said when reached for comment on Monday morning, the school district had not yet been informed of the more than 20 confirmed cases.

�We�ve had no confirmation from the number of cases from DHHS,� Asbell said on Monday.

Asbell said as a precaution the school canceled eighth-grade move up day where students are brought to the high school for a tour. She said the senior class community service day where students volunteer at local schools and retirement homes was also canceled. The last day of school across the district was Monday.

�DHHS recommended we canceled senior service day because the students would be working with vulnerable populations,� Asbell said.

The school notified the state Division of Public Health Services on June 1 after a student was diagnosed with whooping cough. The state DPHS investigates any notification of a whooping cough diagnosis in order to identify whether other individuals may have come in contact with the bacteria and if they require antibiotics.

Pertussis is a bacterial infection of the respiratory tract that can cause a persistent cough, according to DPHS. Early symptoms usually include upper respiratory cold-like symptoms including low-grade fever, cough, and runny nose. These symptoms can last for one to two weeks before progressing to the more typical syndrome that includes intense fits of coughing sometimes with a high-pitched "whoop" and occasionally ending with vomiting, according to the DPHS.

In a letter sent home to parents, the state DPHS said it is working with school officials to identify individuals who may have pertussis or be at risk of developing an infection. The state DPHS is also reaching out to those individuals who have been identified as a higher risk of a pertussis infection in order to recommend antibiotics when needed.

After a person is exposed to pertussis, symptoms usually develop within five to 10 days, but in some cases may not develop for up to 21 days, according to the DPHS. Pertussis is most likely to be passed to other people during the first few weeks a person is ill, according to DPHS. Individuals with pertussis are no longer considered contagious after a five-day course of antibiotics taken to treat the infection, according to DPHS.

There is a vaccine for whooping cough, which is typically administered in four or five doses before a child turns 5. New Hampshire children entering the seventh grade in public school are required by law to get at least one round of the pertussis vaccines, Diphtheria and Tetanus (Tdap Vaccine) on or after their seventh birthday.

According to the Centers for Disease Control roughly eight or nine out of every 10 children who receive five doses of Tdap Vaccines will be generally protected. However, the CDC says the vaccine wanes in its effectiveness as time progresses; protecting seven out of every 10 children five years after their last dose and three to four children out of 10 after 10 years.