In limited ways, MERS can be transmitted through the air

A mystery at the center of the Korean outbreak of Middle East respiratory syndrome (MERS) has been whether the disease has been transmitted through the air.

The authorities have concluded that airborne infection is possible in restricted areas and in wider areas under certain conditions.

Epidemiological investigators at the public-private joint MERS countermeasure headquarters conducted experiments Sunday in Room 8104 of Pyeongtaek St. Mary’s Hospital, where Patient No. 1 stayed from May 15 to 17.

“What we’ve discovered is that when patients sneeze or cough, the virus emitted from them fills up the room,” said an investigator, “and it may be sucked into a hallway or another hospital room when doors or windows are suddenly opened.”

A total of 36 people contracted the disease from Patient No. 1 at the hospital in Pyeongtaek, Gyeonggi, although in nine cases it is uncertain whether they are second- or third-generation infections.

Originally, doctors believed MERS spread in close contact with a patient or direct contact with his or her bodily fluids, including saliva, vomit or feces. In the outbreak of severe acute respiratory syndrome (SARS) in 2003, airborne transmissions were suspected if someone was directly sneezed on or, in the case of an outbreak in Hong Kong’s Amoy Gardens housing estate, through the virus being sucked out of a patient’s residential bathroom by exhaust fans and being sucked into bathrooms in apartments next door or nearby.

In the experiment at Pyeongtaek St. Mary’s Hospital, investigators simulated a patient’s sneeze by blowing pressurized air through special chemicals. They performed common actions like opening and closing doors and windows. The results showed that the particles suspended in the hospital room quickly spread outside.

“We’ve concluded that if the hospital room window is open and wind blows into the room, the virus could have spread along the ward,” said an official.

The Ministry of Health and Welfare previously said that MERS droplets in a sneeze could not be transmitted beyond two meters (6.6 feet).

That did not seem to explain the transmissions in Pyeongtaek St. Mary’s Hospital. Of the 26 patients who directly contracted the disease from Patient No. 1, 22 stayed in other hospital rooms.

The health authority suspected that the air conditioner in Patient No. 1’s room may have played a role because the virus was found on three of its filters. But the possibility of it spreading the disease was ruled out after it was found that the air conditioner was not turned on while Patient No. 1 stayed at the hospital.

The experiment on Sunday gives clues to how MERS spreads.

Another finding showed that water droplets containing the virus could break down and float in the air.

“They are basically aerosols, or made into fine water particles,” another official explained, “and float in the air.”

The experiment proved that droplets on the floor can travel with the wind.

“When Patient No. 1 was most infectious,” said Lee Kwan, a professor of Dongguk University Medical School, “if the virus was smoke, the room would have been filled with thick smoke.”

BY RHEE ESTHER, KIM BONG-MOON [kim.bongmoon@joongang.co.kr]