TAIPEI (Taiwan News) — The Centers for Disease Control announced 17 new cases of whooping cough, bringing the number of domestic cases to 35, the highest over the same period in 10 years. 

CDC Spokesperson Lo Yi-chun (羅一鈞) said at a press conference on Tuesday that the outbreak of the illness, also known as pertussis, was all domestic cases with seven family clusters and one campus cluster, per the CDC.

Lo said the majority of the cases were children aged 11 to 18, accounting for 37%, followed by infants under 6 months old, accounting for 23%. Whooping cough incidence typically reflects this demographic as infants have yet to receive vaccine protection, and adolescents are more vulnerable as vaccine protection weakens.

Whooping cough cases have been on the rise domestically since May, with Japan also experiencing a severe whooping cough outbreak with more than 30,000 cases this year, seven times the total number of cases reported for 2024.

Lin Yung-ching (林詠青), an epidemic prevention physician at the CDC, said a northern cluster began with a teenage boy who developed a cough and a runny nose in late May. He tested positive for the illness after seeking medical treatment in early June.

His four family members and four classmates were also tested positive, bringing the total infected to six men and three women, five of whom had been vaccinated. A total of 145 contacts were identified and are being monitored until July 10.

Lo said another case involved a woman in her 70s who began to experience breathing difficulty in late May. As her symptoms worsened, she sought medical treatment in mid-June and was diagnosed with whooping cough.

An epidemiological investigation found two family members who lived with her had symptoms. Both were confirmed positive by health authorities and have been given medication, with six contacts identified and monitored until July 16.

Lin said the family cluster in central Taiwan consists of a one-month-old baby boy and his mother, a woman in her 20s. The baby began to cough, vomit, and spit up milk in early June. He later went to the hospital, where he tested positive.

An epidemiological investigation found that his mother had symptoms in late May and has tested positive. The baby boy remains hospitalized, but his condition is stable as five family members are being monitored until July 15.

The family cluster in the south is a woman in her 50s with a history of multiple chronic diseases and her mother, a woman in her 80s. Lin said the younger woman started coughing in early June, and her illness gradually worsened, requiring hospitalization in mid-June when she was diagnosed.

Her condition has since improved, and she has been discharged. Her mother had similar coughing symptoms and was given medication. The three family members living there will be monitored until July 24.

Severe whooping cough in infants under six months old may lead to pneumonia and encephalitis. The mortality rate of unvaccinated infants is about 1% to 3%. Whooping cough symptoms in adolescents and adults may be relatively mild, though they are the main source of pertussis transmission to infants.

The domestic vaccination schedule for whooping cough consists of a total of five doses: one dose of the five-in-one vaccine each at two, four, six, and 18 months, with an additional dose from the age of five to before entering elementary school.

Parents are encouraged to take their infants and young children to get timely vaccinations. Adolescents aged 11 to 18 are encouraged to get an additional dose of the combination vaccine that also covers tetanus and diphtheria.