South Korea believes its MERS virus outbreak may have peaked.

Experts say the next few days will be critical to determining whether the government's belated efforts have successfully stymied a disease that has killed seven people and infected nearly 100 in the country.

The maximum incubation period for those infected by a second "super-spreader" ends around Friday, experts said, raising hopes that the outbreak could weaken soon.

"I cautiously predict (MERS) will peak today" and be stabilized in the next few days, Health Minister Moon Hyung-pyo told lawmakers on Monday.

The biggest outbreak of Middle East respiratory syndrome outside the region where it was first seen in 2012 was introduced to South Korea last month by a 68-year-old man who had traveled to Saudi Arabia and other nearby countries.

When he became sick after returning to South Korea, he visited several hospitals and clinics, where dozens of other patients and hospital workers were infected before officials determined he had MERS.

The government began gradually isolating victims and quarantining those who had contact with them.

There have been widespread fears in South Korea about the poorly understood disease, which has no vaccine and a mortality rate as high as 40 percent.

There has also been growing criticism over failures by health workers and the government to initially recognize and quickly contain the disease.

Nearly 3,000 people have been placed in isolation and 2,200 schools closed in South Korea.

Although MERS spreads through close contact with people who are sick - not through the air - many have avoided going to crowded places like baseball parks and movie theaters. Travel agencies report a sharp increase in the number of foreigners canceling plans to visit South Korea.

However, so far the outbreak has been contained in hospitals and there is no evidence of sustained transmission in the community, the UN health agency said.

Authorities said the first MERS patient did not disclose his trip to Saudi Arabia to doctors until he arrived at the Samsung Medical Center in Seoul after being treated at three other hospitals, including St. Mary's Hospital in Pyeongtaek, south of Seoul. Samsung and St. Mary's have seen most of the country's infections.

The patient's wife, who was the country's second MERS case and is now out of the hospital, told a local TV station that her husband did not intend to hide information about his travels, but simply had trouble talking to doctors because of his high fever.

Because the virus' incubation period is estimated at five to six days on average, extending up to about two weeks, experts believe there won't be any more cases infected directly by the first patient. The Health Ministry said that no more MERS cases have originated from St. Mary's Hospital.

There are still concerns about Samsung Medical Center, where at least 37 people have been infected, although fewer cases have been reported there in recent days.