South Korean President Park Geun-hye said on Wednesday that everything must be done to stop Middle East respiratory syndrome, as fear of the disease shut hundreds of schools and led to corporate giant Samsung calling off a staff conference.

Five more cases were confirmed on Wednesday, bringing to 30 the number infected in South Korea since the outbreak began there two weeks ago. Two people have died, fueling fear in the country with the most cases outside the Middle East, where the disease first appeared.

While there has been no sustained human-to-human transmission, the nightmare scenario is the virus changes and spreads rapidly, as SARS did in 2002 and 2003, killing about 800 people worldwide.