太陽光でコロナ不活性化、米政府が詳細公表

【ワシントンＡＦＰ＝時事】米国土安全保障省は28日、AFPに対し、新型コロナウイルスが太陽光によって急速に不活性化するとした研究結果をめぐる詳細の一部を公表した。実験では自然の太陽光を正確に再現したとしている。（写真は資料写真）
　米ホワイトハウスが先週発表した研究結果の概要には大きな期待が寄せられた一方、一部の専門家からは、より包括的な報告が公表されるまで慎重になるべきだとの声も上がっていた。
　国土安全保障省のウィリアム・ブライアン氏は先週の記者会見で、無孔質の表面にあるウイルスの量は、温度２１～２４度および湿度８０％で太陽光があると、わずか２分で半減すると説明。空気中に漂うウイルスの量についても、通常の室温・湿度２０％の環境に太陽光が当たると、わずか１分半で半減すると述べた。
　この発表は、専門家らを驚かせた。米コロンビア大学メディカルセンターの放射線研究センターで所長を務めるデービッド・ブレナー氏がＡＦＰに語ったところによると、太陽光に含まれる紫外線の多くは紫外線Ａ波（ＵＶＡ）に分類され、ＵＶＡは日焼けや肌の老化の原因となるが、ウイルスに有害であるとは一般的に証明されていない。
　一方で紫外線の一つであるＣ波（ＵＶＣ）は、動物細胞やウイルスの遺伝物質を傷つける性質が特に強く、殺菌ライトにも広く使用されている。しかし、大気に吸収されるため、地上に到達する太陽光内には存在しない。
　今回の研究の指揮を執った国土安全保障省の科学者ロイド・ハフ氏は、研究で使用した紫外線ライトの種類について「自然の太陽光に近いものに設定した」と説明。具体的には、北緯４０度や大西洋中央部などの中緯度地域において、立夏の正午ごろに海抜ゼロ地点でみられる太陽光を想定したという。
　また国土安全保障省の報道官によると、ステンレス鋼の表面上に付着した疑似唾液の飛沫（ひまつ）でも実験が行われた。研究論文は間もなく査読され、科学雑誌に掲載されるという。【翻訳編集ＡＦＰＢＢＮｅｗｓ】
〔ＡＦＰ＝時事〕（2020/04/30-12:57）

The US Department of Homeland Security revealed to AFP on Tuesday new technical details regarding its highly anticipated study into how ultraviolet radiation destroys the new coronavirus, saying that its experiment had accurately mimicked natural sunlight.
A summary of the research was presented last week at the White House, with some scientists calling for caution until a more comprehensive report was made public.
US President Donald Trump raised eyebrows last week when he used his daily live national press briefing to ask whether light could become a medical treatment.
Supposing we hit the body with a tremendous -- whether it's ultraviolet or just very powerful light, he said. Supposing you brought the light inside the body, which you can do either through the skin or in some other way.
Trump continued on to suggest that people inject disinfectants to cure the virus, an idea that health experts quickly shot down.
DHS official William Bryan had briefed the media that the amount of virus on a non-porous surface shrunk by half in just two minutes when sunlight was present, the temperature was 70-75 degrees Fahrenheit (21-24 Celsius) and humidity was 80 percent.
The amount of virus suspended in air shrunk to half its amount in just 1.5 minutes at room temperature and 20 percent humidity, he added.
These eye-catching results surprised experts because most of the UV light contained in natural sunlight belongs to a subtype called UVA, which causes human skin to tan and age but has not generally been proven harmful to viruses, David Brenner, director of the Center for Radiological Research at Columbia University Medical Center, told AFP.
On the other hand, a part of the spectrum called UVC is particularly adept at warping the genetic material of animal and virus cells and is widely used in sterilizing lamps, but it is not present in sunlight because it is filtered out by the Earth's atmosphere.
Asked for further details on the type of UV light that was used, Lloyd Hough, a DHS scientist overseeing the test, said: The spectrum of light that was used was designed to approximate natural sunlight that you would expect to see at noon at sea level at a mid-latitude location (e.g., mid-Atlantic, 40 degrees N) on the first day of summer.
More specifically, it approximates the wavelengths of light predicted by the National Center for Atmospheric Research's (NCAR) Tropospheric Ultraviolet and Visible (TUV) Radiation Model for noon at 40 degrees N latitude at sea level on June 21st in range of 280 and 400 nanometer wavelengths.
The wavelengths specified pertain only to long- and medium-wave ultraviolet, also known as UVA and UVB -- the UV components of sunlight that penetrate the atmosphere -- and not UVC.
- Paper coming soon -
A DHS spokesman added that the test -- which was conducted at the National Biodefense Analysis and Countermeasures Center in Maryland -- was carried out on droplets of simulated saliva on a stainless steel surface.
Brenner, who is himself performing research into another area of the UV spectrum called far-UVC, which kills microbes without penetrating human skin, said the DHS findings did not comport with previous research.
There is a peer-reviewed paper in the literature from the FDA (Food and Drug Administration) showing the earlier SARS-CoV virus did not respond to UVA light (though it did respond to UVC light), he said, adding it is reasonable to assume that all coronaviruses respond roughly the same way to light.
The results as presented were straining credulity, he added.
But a DHS spokesman said that study would soon be submitted for peer review and published in scientific journals.
While the results are still undergoing a rigorous scientific review, we felt it important to share information on the emerging trends that are being identified in our tests, the spokesman said.