Japan confirmed dozens more swine flu cases overnight, bringing its tally to 176, health officials said Tuesday, as the government considered scaling down quarantine checks at airports while focusing on its domestic outbreak. The outbreak in Japan surged from just four cases over the weekend after infections were confirmed in the port city of Kobe and nearby Osaka, which is Japan's second-biggest urban area. The 41 added to the list overnight included high school students and small children as the outbreak jumped to three more cities in the region. The new wave of infections did not have a clear connection to foreign travel, as the initial one did, and involved primarily teenagers. None of the patients were in serious condition. The number could climb further because medical institutions around the country are now testing viral samples of suspected patients with no foreign travel records, who were previously excluded from testing. Health and Welfare Minister Yoichi Masuzoe indicated that airport quarantine efforts would be scaled down and urged flexibility in anti-flu measures because the swine flu, formally known as A(H1N1), is now believed to be no more infectious than seasonal influenza. The chief cabinet secretary, Takeo Kawamura, said at a news conference: "We need to prevent the infections from spreading further, we must also maintain public activities." He said the government will "phase out" airport quarantine checks. However, the government said it would do its best to quell the spread of the disease and keep schools shut at least- through the end of the week. Companies discouraged unnecessary business trips, and schools have canceled excursions. Visitors to Parliament and other government offices have been asked to wear surgical masks and rub their hands with disinfectant gel before entry. Reports said dozens of the students had played in school volleyball games, but officials could not confirm whether that had any relation to their infections. Experts also suspect that a domestic outbreak may have been triggered silently weeks before Japan caught its first cases at its main airport in early May. Japan now ranks as the fourth-most infected country in the world, after Mexico, the United States and Canada, according to Japanese media reports. Seoul confirms 4th case The South Korean authorities say tests confirm that a Vietnamese traveler has swine flu, The Associated Press reported from Seoul. The 22-year-old was quarantined at Incheon International Airport on Sunday after arriving from Seattle with a fever. She had been planning to catch a connecting flight to Vietnam. The Centers for Disease Control and Prevention in South Korea confirmed that she had the virus. It's the fourth con-finned case of the new flu virus in South Korea. The others have recovered.