Spike in virus cases shows perils of reopening

South Korea considers reimposing social distancing restrictions.

SEOUL, SOUTH KOREA — As Mediterranean beaches and Las Vegas casinos laid out plans to welcome tourists again, South Korea announced a spike in new infections Wednesday and considered reimposing social distancing restrictions, revealing the setbacks ahead for other nations on the road to reopening.

Forty newly confirmed cases — the biggest daily jump in nearly 50 days — raised alarms as millions of children returned to school Wednesday.

All but four of the new cases were in the densely populated Seoul region, where officials are scrambling to stop transmissions linked to nightclubs, karaoke rooms and a massive e-commerce warehouse.

All were reopened last month when social distancing measures were relaxed.

The country’s top infectious disease expert said South Korea may need to reimpose social distancing restrictions because it’s becoming increasingly difficult for health workers to track the spread of COVID-19 amid warmer weather and eased attitudes on distancing.

“We will do our best to trace contacts and implement preventive measures, but there’s a limit to such efforts,” said Jeong Eunkyeong, director of South Korea’s Centers for Disease Control and Prevention.

“Young people have a very broad range of activity, so at the point of diagnosis, there’s already a lot of exposure . ... The number of people or locations we have to trace are increasing geometrically,” he added.

Seoul and nearby cities in recent weeks have re-closed thousands of bars, karaoke rooms and other entertainment venues to slow the spread of the virus.

U.S. officials are pushing hard to reopen even as more than a dozen states are still seeing increasing new cases.

Nevada Gov. Steve Sisolak announced Tuesday night that casinos can reopen after a 10-week shutdown on June 4, welcoming tourists to the gambling mecca of Las Vegas. Sisolak had planned to make the announcement at a news conference but scrapped the live event after he learned he was potentially exposed to the virus at a workplace visit.

AHN YOUNG-JOON / AP People walk along the Cheonggye Stream in Seoul, South Korea, last week. The country’s top infectious disease expert said South Korea may need to reimpose social distancing restrictions because it’s difficult to track the spread of COVID-19 amid warmer weather and eased attitudes on distancing.