The World Health Organization warned that the MERS outbreak in South Korea is likely to grow, as the number of people under quarantine crept up to 1,369 on Wednesday, with 30 confirmed cases of the disease.

So far, two people have died after contracting the respiratory virus in South Korea in the largest MERS outbreak outside Saudi Arabia. The vast majority of the South Korean cases have been linked to infections from hospitals.

More than 540 schools have shut to prevent the spread of the virus, according to South Korea’s education ministry.