患者から４メートル離れた空気中に新型ウイルス、推奨対人距離の２倍

【ワシントンＡＦＰ＝時事】新型コロナウイルス感染症（COVID-19）患者の病棟で採取した空気サンプルの調査で、新型ウイルスは最大4メートル飛散することが分かった。現在推奨されている確保すべき対人距離の2倍に相当する。中国の研究者らが10日、調査の予備段階の結果を米疾病対策センター（CDC）のオンライン雑誌「新興再興感染症雑誌」で発表した。（写真は資料写真）
　中国・北京の軍事医学研究院が主導する研究者らは、２月１９日から３月２日まで、中国・武漢の火神山医院の集中治療室と新型肺炎患者用の一般病棟で物体の表面のサンプルと空気のサンプルを採取した。
　研究チームが着目したのは、いわゆる「エーロゾル（エアロゾル）感染」だ。せきやくしゃみの飛沫（ひまつ）は数秒以内に地面に落下するが、ウイルスが超微細な霧状の粒子である場合は、空気中に数時間浮遊する。
　研究チームは、ウイルスを含んだエーロゾルが主に患者の近くおよび風下側最大４メートルの位置に集中していることを確認。患者の風上側では最大約２．４メートルの位置まで確認できた。
　病院の医療従事者には一人も感染者が出ていないことから、論文の執筆者らは、「適切な予防策を講じれば、感染を効果的に防止できることを示している」としている。
　超微細な霧状の粒子に含まれるわずかな量の新型ウイルスの感染力がどの程度かはまだ明らかになっていないため、新型ウイルスのエーロゾル化については研究者らの間で議論を呼んでいる。論文は、新型肺炎の感染の仕組みについての議論に影響を与える内容だが、中国の研究チームは、今回調査した距離で検出された少量のウイルスで感染するとは限らないとしている。【翻訳編集ＡＦＰＢＢＮｅｗｓ】
〔ＡＦＰ＝時事〕（2020/04/13-13:17）

A new study examining air samples from hospital wards with COVID-19 patients has found the virus can travel up to 13 feet (four meters) -- twice the distance current guidelines say people should leave between themselves in public.
The preliminary results of the investigation by Chinese researchers were published Friday in Emerging Infectious Diseases, a journal of the US Centers for Disease Control and Prevention (CDC).
They add to a growing debate on how the disease is transmitted, with the scientists themselves cautioning that the small quantities of virus they found at this distance are not necessarily infectious.
The researchers, led by a team at the Academy of Military Medical Sciences in Beijing, tested surface and air samples from an intensive care unit and a general COVID-19 ward at Huoshenshan Hospital in Wuhan. They housed a total of 24 patients between February 19 and March 2.
They found that the virus was most heavily concentrated on the floors of the wards, perhaps because of gravity and air flow causing most virus droplets to float to the ground.
High levels were also found on frequently touched surfaces like computer mice, trashcans, bed rails and door knobs.
Furthermore, half of the samples from the soles of the ICU medical staff shoes tested positive, the team wrote. Therefore, the soles of medical staff shoes might function as carriers.
- Airborne threat? -
The team also looked at so-called aerosol transmission -- when the droplets of the virus are so fine they become suspended and remain airborne for several hours, unlike cough or sneeze droplets that fall to the ground within seconds.
They found that virus-laden aerosols were mainly concentrated near and downstream from patients at up to 13 feet -- though smaller quantities were found upstream, up to eight feet.
Encouragingly, no members of the hospital staff were infected, indicating that appropriate precautions could effectively prevent infection, the authors wrote.
They also offered advice that bucks orthodox guidelines: Our findings suggest that home isolation of persons with suspected COVID-19 might not be a good control strategy given the levels of environmental contamination.
Aerosolization of the coronavirus is a contentious area for scientists who study it, because it is not clear how infectious the disease is in the tiny quantities found in ultrafine mist.
The World Health Organization has so far downplayed the risk.
US health authorities have adopted a more cautious line and urged people to cover their faces when out in public in case the virus can be transmitted through normal breathing and speaking.