56 coronavirus cases were linked to a Starbucks in South Korea. But employees who were wearing masks didn't get infected.

• At least 56 coronavirus cases have been linked to a Starbucks in Paju, South Korea.

• Health officials attributed the outbreak to customers not wearing face masks and a lack of proper ventilation inside the store, possibly related to the air-conditioning.

• None of the employees, who were wearing masks during their shifts, were infected.

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At least 56 coronavirus cases in South Korea have been linked to a Starbucks in Paju. Many customers were not wearing masks, and the poorly ventilated space likely contributed to the spread of the virus, local news reports said.

But the four employees were not infected, and experts think it's because they were wearing masks during their shifts.

Health officials said the outbreak originated from a person infected with the virus who sat in the cafe earlier this month next to the air-conditioning system, which dispersed contagious aerosol particles throughout the space, Arirang News reported. The virus also could have spread as people touched contaminated surfaces such as tables and door handles, they said.

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"Many of the visitors didn't wear masks, and there seems to be no proper air ventilation at the store even though air conditioners were in operation due to humid weather," Jeong Eun-kyeong, the chief of the Korea Centers for Disease Control and Prevention, said of the outbreak, according to the Yonhap News Agency.

"Even if infections did not occur via aerosol transmission, droplet transmission is also possible in a confined space, and the virus could have spread via hand contact."

South Korea had more success than many countries in containing the virus, implementing meticulous tracking and testing measures earlier this year, though it saw a resurgence of the virus this summer.

The recent spike in cases has led health and government officials to mandate mask-wearing and consider more intensive social-distancing measures to control the outbreaks, Reuters reported on Sunday.

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