Marin County health officials have issued a whooping cough advisory due to an on-going outbreak that appears to be having a large impact at Tamalpais High School. Last Friday, Public Health Officer Dr. Matt Willis sent the advisory and noted that the county's Department of Health and Human Services had investigated 77 cases of whooping cough, or pertussis, since December. On Thursday, the department said 36 additional cases have come to light. "So far, Marin County has investigated 113 cases of Pertussis from mid-December to today. Most of the cases are clustered in the South Marin area, including an outbreak at Tamalpais High School with (more than) 65 cases identified," the county's Senior Public Health Nurse Lindsey Termini said in an email. "Pertussis typically surges every 3-5 years. The last surge in Marin County was in 2018, with >300 cases in the community identified." As of Thursday, there were no reported cases of hospitalizations due to whooping cough in the county and no reported infant cases. "We are working closely with Tam High to help mitigate spread by releasing exposure notifications," Termini said. She said that the infection spreads easily from person to person through droplets in the air and is usually milder in teens and adults than in babies and children, especially those vaccinated against whooping cough. Symptoms can seem like the common cold and include fatigue, runny nose, sneezing and a mild cough that can eventually progress to severe coughing fits. It's also not uncommon for high school-aged adolescents to contract the illness at higher rates since their childhood whooping cough vaccinations are becoming less effective. "In Marin County, our primary focus is protecting infants and people at high risk of getting sick," Termini said. "The best thing people can do to protect themselves is to ensure they are up to date on the pertussis vaccination, practice proper respiratory and hand hygiene, and stay home if they are sick." People diagnosed with whooping cough should stay home for 21 days after coughing begins or for five days after the start of antibiotics. For more information about the county's whooping cough response, people can visit https://www.marinhhs.org/pertussis . Administrators with Tamalpais High School and the Tamalpais Union High School District didn't immediately respond to a request for comment.