The fatal outbreak of Middle East respiratory syndrome in South Korea has so far been contained to hospital transmissions, but it's possible the virus could spread in the community, so continued vigilance is necessary, a senior World Health Organization official said.

Keiji Fukuda, assistant director-general of the UN health agency, made the remarks after assessing the situation firsthand. The MERS outbreak in South Korea is the largest outside of Saudi Arabia and has so far infected more than 180 people, killing 31.

"Right now, we don't see any evidence of the virus causing sustainable transmissions among humans or in the community," Fukuda said. "It, however, won't be surprising if we see some transmissions and cases in the future outside of the healthcare settings, and we had seen that occurring in the Middle East before."