This Oct. 5, 2022, file photo shows a child receiving a flu vaccine shot at a clinic in Seoul. The number of whooping cough cases has reached its highest level in more than 20 years in Korea as health authorities called on Friday for greater precautions and expanded vaccination programs. Newsis

The number of whooping cough cases has reached its highest level in more than 20 years in Korea as health authorities call for greater precautions and expanded vaccination programs.

According to the Korea Disease Control and Prevention Agency on Friday, 1,365 people have been infected with the highly contagious respiratory disease as of June 1.

The figure has already exceeded the annual total of 292 last year and is higher than any year since 2001, the earliest year for which data is available.

Minors are the most vulnerable group, data shows. Those aged between 13 and 19 account for 49.6 percent of the confirmed cases this year, while children aged between seven and 12 account for 37.5 percent.

By region, 39.8 percent of cases were reported as occurring in South Gyeongsang Province, followed by Gyeonggi Province (17.4 percent), Busan (8 percent) and North Gyeongsang Province (6.6 percent).

The first signs of whooping cough, also known as pertussis, are similar to those of a cold, like a runny nose and sore throat. In about a week or two, the patient may develop more serious symptoms such as uncontrollable coughing that ends with a high-pitched "whoop" sound and vomiting among others. The cough may last for several weeks or even months.

Health officials in other countries are also scrambling to curb their rising cases of the disease. There have been at least 4,864 whooping cough cases reported in the U.S. this year. This is nearly three times higher than the 1,746 cases reported in 2023 during the same period. In China, more than 90,000 cases were reported this April alone.

Whooping cough can be life-threatening for babies younger than six months. But over the last decade, no deaths, caused by the disease, have been reported in Korea, thanks to the high vaccination rate among infants here ― higher than 97 percent.

Officials at the health agency have urged parents and teachers of young children to pay extra attention to their health condition, saying that those who have not been vaccinated should start their vaccine series to minimize the risk of severe complications if infected.