By Bae Ji-sook
Staff Reporter

The World Choir Championship 2009, which opened Wednesday in Changwon, South Gyeongsang Province, was canceled Friday after 13 participants from Indonesia and one Korean volunteer were found to have possibly contracted influenza A (H1N1), and had to be hospitalized.

Meanwhile, the Korea Centers for Disease Control and Management (KCDC) advised vacation goers to refrain from visiting crowded places.

The authorities are worried about the possibility that large events over the summer holidays will turn into routes for possible mass transmission of the virus.

So far this month, 13 people have already been confirmed with the infection. All of them are suspected of having contracted the virus at events involving people who have been abroad.

Five members of a group of 45 Christians were confirmed with the virus after a trip to Thailand from June 17 to July 2. Two university students were confirmed after returning from a trip to the Philippines from June 24 to July 4.

In addition, another two patients were diagnosed with the disease after attending a large camp where 8,500 university students from more than four countries gathered for four days. The disease center assumes that all attendees may have been exposed to the virus.

Meanwhile, the first case of influenza A among local residents to have an undetermined location of transmission was reported Friday, according to the KCDC.

A 36-year-old woman was recently confirmed to have contracted the disease after suffering from a high fever since July 2, it said. However, the KCDC could not determine where the woman, a nursery school teacher, became infected. She had never been abroad and had not been in the vicinity of a patient with the new strain of influenza.

It surmised that she may have visited crowded places and contracted the virus from a stranger.

The woman is now in isolation and the government has recommended that her family members and students refrain from going outside for seven days.

``If you have been to large events and have a runny nose, high fever or sore throat, please report to the nearest public healthcare center,'' Shin Sang-sook, a ministry official, said.

So far, Korea has confirmed 367 cases of the influenza infection with 91 remaining hospitalized.

bjs@koreatimes.co.kr