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Experts urging social distance as coronavirus clusters multiply, diversify in Japan

Commuters cross a street near JR Osaka Station in the city of Osaka on April 5, 2021, the first day of a coronavirus quasi-emergency covering the municipality and five other cities in Japan. (Mainichi/Kenji Ikai)

TOKYO -- Coronavirus quasi-emergencies have gone into effect in six Japanese cities in three prefectures -- Osaka, Hyogo and Miyagi -- with sudden infection surges. The new municipal-level measures include shortened business hour requests for restaurants and bars, but also demand that people refrain from frequenting karaoke spots, which the previous states of emergency had not. Behind these developments lies a shift in the structure of the pandemic: cluster infections are diversifying.

    On April 1, the day of the decision to apply core quasi-emergency anti-infection measures, the government's Advisory Committee on the Basic Action Policy's chairman Shigeru Omi told reporters, "The places where transmissions happen change frequently. Cluster infection sites are diversifying, into student get-togethers, places that attract crowds, factories, foreign resident communities, and so on."

    Reports of cluster infections traced to places other than eateries are trending upward. One example is "karaoke clusters," or clusters among mostly elderly people who get together for karaoke in the middle of the afternoon. In southwest Japan's Fukuoka Prefecture, there have been four karaoke-related clusters reported since the end of February this year.

    It is difficult for establishments offering karaoke to keep their doors and windows open due to noise concerns, while singing can produce more airborne liquid droplets than talking. In one, six-person cluster confirmed in Ogori, Fukuoka Prefecture, the people had apparently taken their masks off to sing in an insufficiently ventilated space.

    In the northern city of Aomori in March, 25 people were infected in a cluster traced to a real estate agency introducing rentals, eight of them customers or employees, according to Aomori Prefecture and other sources. A male customer in his 40s was confirmed infected on March 18 after complaining of a fever and fatigue, and the agency emerged as a potential transmission site after authorities traced the man's movements over the previous 14 days. PCR testing was carried out on the employees and other people connected to the case from the following day, and the cluster was confirmed.

    The real estate agency apparently had been taking anti-infection precautions, including keeping the office well ventilated and requiring workers to wear masks.

    "At real estate agencies, there are times when customers and employees are quite close to each other when speaking while looking at floor plans, or taking the same car to go look at properties," noted an Aomori municipal public health center representative overseeing the case. "It's important for both parties to keep a certain distance from one another."

    If a cluster occurs just once in a spot where large, unmanaged crowds congregate, the number of related infections tends to spike dramatically.

    In a cluster tied to a February sales event run by a food company in the northern city of Sapporo, 28 of the 42 event participants were infected with the coronavirus. Among them were some who had come from outside Hokkaido. It was confirmed later that the group had been infected with one of the coronavirus variants, which are suspected of spreading more quickly than the original.

    In total, 32 of the total 63 people at the event were infected, including the organizer and guests. Just as with the real estate agency, the organizers had anti-infection measures in place, including a mask requirement and hand sanitizer on-site. However, according to the city of Sapporo, attendees took off their masks at the tea and coffee corner, while some people got close together during business meetings at the event.

    "Infection risk does not go down to zero even if you wear a mask," said the Sapporo official handling the case. "I'd like people to wear masks properly, and avoid talking loudly or in close proximity to others."

    There are also cases of clusters outdoors. Japan's economic revitalization minister Yasutoshi Nishimura stated in an April 4 news program on public broadcaster NHK, "Air circulation is indeed good outside. But there have been clusters traced to outdoor barbecues or sidewalk drinking parties. I'd like people to understand that, basically, the infection spreads through airborne droplets."

    Koji Wada, a professor of public health at the International University of Health and Welfare, told the Mainichi Shimbun, "Among the 'three Cs' of confined spaces, crowded places and close contact, the one most often forgotten is close contact. I want people to be conscious once again of the fact that infection risk from airborne droplets rises if you speak close up with someone, or in a loud voice."

    The close of Japan's fiscal year at the end of March brought with it its usual flurry of movement as people started at new companies, new posts and new schools. This in turn created a flood of opportunities to meet new people.

    According to research by University of Tokyo professor Yukio Osawa and others, infection risk rises when meeting people outside your normal circle of family and friends. Meanwhile, one member of an expert advisory board to the health ministry stated, "The trigger for infections is not just limited to going out at night, or happening at restaurants and bars. Transmission is also happening in situations that fall beyond the early closing requests, such as afternoon drinking parties. As much as is feasible, I want people to cease gathering in groups."

    (Japanese original by Sooryeon Kim and Natsuko Ishida, Lifestyle and Medical News Department)

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