South Korea recorded the largest number of measles cases in six years, adding to concerns that the combination of low vaccination rates with international travel will help further outbreaks elsewhere in the region.

The South Korean Disease Control and Prevention Agency (KDCA) said this week that the country has confirmed 52 cases so far this year, surpassing the 49 cases recorded in all 2024. This is the highest number since 2019, when 194 cases were recorded.

The World Health Organization (WHO) recognized South Korea as "measles-free" in 2014, but believed that overseas travel and aging population led to an increase in cases.

South Korea is not alone in its measles outbreak, which experts believe is the most infectious disease. In the United States, with the outbreaks in Texas and Thailand and Vietnam, the alarm is getting bigger and bigger. The United States will suffer the biggest measles outbreak in a quarter of a century, with one of the leading immunologists warning: “We live in the latter’s immune world.”

Vietnam's health ministry said officials have identified about 40,000 suspected measles cases and five deaths this year, prompting calls for speeding up vaccination in children. According to media reports, Vietnam confirmed 6,725 cases and 13 deaths in 2024 - the majority of deaths occur in children and older people with underlying health conditions, according to media reports.

According to data reported to the WHO by member states, Thailand had 7,507 cases in 2024, compared with only 38 in 2023.

The outbreak in South Korea is attributed to uninoculated travelers overseas. Yonhap News Agency said that of the 52 cases reported by KDCA this week, 34 people from overseas (mainly from Vietnam).

"The global increase in measles may lead to more import cases," a KDCA official told Yonhap. "The risk of a rapid outbreak remains low due to our stable vaccination rates and monitoring systems."

According to infectious disease experts, two doses of measles vaccination during childhood are about 99% effective in preventing someone.

"The latest data suggests that the measles outbreak is still underway in Vietnam and we are seeing a continuing trend in cases in central and northern Vietnam, including new outbreaks of cases or case groups that have not been reported in parts of the country.

It added: “Many children who are not vaccinated or under-vaccinated are exposed to infection due to the high infectivity of measles and significant immunity gap.”

Outbreaks in the United States and Southeast Asia have attracted attention that Australia could also become a "fertile land" for the disease.

According to a situation on the Centers for Disease Control and Prevention website, measles can cause serious complications in vulnerable children and adults, including pneumonia, encephalitis, and death.