The number of shingles infections has been climbing in South Korea, data showed on Thursday.

According to the National Health Insurance Corporation, a total of 722,257 people were infected with the disease in 2021, a 2.4 percent increase from 705,661 in 2017.

The total amount of medical expenses related to the disease borne by individuals, families and the Korean government amounted to 166.1 billion won ($125 million) in 2021, an 11.9 percent increase from 2017.

Chances of getting infected with shingles are higher for those over 50. Of all the age groups, people in their 60s constituted the largest share of the total number of shingles patients at 23.8 percent, followed by those in their 50s with 22.4 percent and those in their 40s with 15.9 percent in 2021.

“Anyone who has had chickenpox can get shingles, however, the risk of developing shingles increases with age. Most people get shingles in their 50s or later in life,” said Kang Yeon-seung, a professor of anesthesiology at Ilsan Hospital, a facility run by the National Health Insurance Corporation.

“Because anyone with a weakened immune system has an increased risk of getting shingles, it is important to work out regularly. Regular exercise can improve one‘s immune system.”

Shingles, also known as herpes zoster, is an illness caused by the varicella zoster virus. It occurs in people who have previously had chickenpox, when the virus is reactivated in the nerve cells. It is said that older adults and people with weakened immune systems are more likely to get shingles. Shingles causes a painful blistering dermatomal rash.

Two live virus vaccines (Zostavax and SKYzoster) are commonly available in Korea, and adjuvanted recombinant zoster vaccine Shingrix was newly introduced at the end of last year. Some local governments offer them for free to those aged 65 and over, or to low-income groups.

Shingles infection rates have been increasing throughout the world, though the exact reasons for this are unclear. It is believed that it is increasing rapidly due to the aging population.