Schools across Korea are on high alert as cases of whooping cough, a highly contagious respiratory illness, surge among students in different regions.

Daegu city government officials reported 73 cases of the respiratory disease as of last Thursday, the highest number in the past decade. This is a significant increase from the four cases reported in all of last year.

Of the 73 cases, 65 involve students from elementary, middle and high schools in Daegu.

Whooping cough, also known as pertussis or “100-day cough,” typically begins with symptoms similar to a common cold, such as a runny nose and sore throat. It spreads when a person inhales bacteria-containing droplets in the air, typically from the coughs and sneezes of infected individuals.

After one to two weeks, the illness can progress to more severe symptoms, including intense coughing with a distinctive whooping sound, which may be followed by vomiting. These coughing episodes can last for several weeks or even months.

The Gangwon Provincial Office of Education also announced Tuesday that it would strengthen sanitation measures after 75 students from 7 different elementary schools in the city were found to have been infected.

Last week, the Korea Disease Control and Prevention Agency called for vigilance against whooping cough, noting a more than threefold increase in cases over the past four weeks, particularly among children and adolescents.

Nationwide, cases rose from around 210 at the end of last month to 678 by the third week of this month.

"Because young children are more easily susceptible to severe complications from whooping cough, please ensure they are fully vaccinated and take other preventive measures," the KDCA urged.