SEOUL, SOUTH KOREA: South Korea on Wednesday declared a formal end to an outbreak of the MERS virus that killed 38 people and sickened dozens of others since May.

The announcement by South Korea's Health Ministry came a month after the last infected patient in the country died.

Health officials said the announcement is in line with international standards that require 28 days to pass with no new cases. That's twice the maximum incubation period of the virus that causes Middle East Respiratory Syndrome.

Since the outbreak started in May, 186 people in South Korea were infected. More than 16,000 people were isolated at hospitals or homes as authorities struggled to stop the disease's spread.

MERS, discovered in 2012, is caused by a coronavirus in the same family as the common cold and SARS.

The virus usually does not spread easily, but experts suspect crowded emergency rooms and hospital wards might have contributed to a wider-than-expected transmission in South Korea. South Koreans' habits of "doctor shopping" — visiting multiple facilities to treat the same illness — and having many friends and relatives visit hospitalised patients also might have contributed.