Another student who took part in a school trip to Canada has swine flu, the fourth confirmed case in Japan, the health ministry said May 10.

The 16-year-old boy was on board the same flight as a teacher and two other students who were confirmed May 9 as Japan's first cases of the H1N1 influenza A virus.

According to the Osaka Prefectural Board of Education, the student arrived at Narita from Detroit on May 8 together with the three infected passengers — a 46-year-old teacher and two 16-year-old students — after staying in Oakville, Ontario, from April 24 on a school trip.

During quarantine inspection after landing, the student exhibited no flu symptoms but later complained of fever and coughing after being taken to a hotel for medical monitoring. He was among 49 people subject to medical monitoring, including 33 who traveled with the three confirmed cases on the school program.