A team of scientists from the University of California San Diego, Caltech and Texas A&M remotely put their heads together to analyze the transmission pathways of COVID-19. Their study confirms that face coverings determine the pandemic’s trends and significantly reduce the number of infections.
来自加州大学圣地亚哥分校(University of California San Diego)、加州理工学院(Caltech)和德州农工大学(Texas A&M)的一群科学家们远程交流和分析COVID-19的传播途径。他们的研究证实，口罩决定了COVID-19大流行的趋势，并显著减少了感染人数。
（图1所示。COVID-19大流行的全球趋势明显。）
Examining trends and mitigation measures in three epicenters — Wuhan, China; Italy and New York City — the scientists’ study, published recently in PNAS, shows that airborne transmission is the highly virulent and dominant route for spreading COVID-19. At the same time, the study shows that other mitigation measures, such as social-distancing and shelter-in-place, insufficiently protect the public.
审查三个中心的趋势和缓解规定——中国武汉；意大利和纽约市——科学家最近发表在《美国国家科学院院刊》(PNAS)上的研究表明，空气传播是COVID-19的高毒性和主要传播途径。与此同时，研究表明，其他缓解规定，如社交距离及就地避难，不足以完全保护公众。
“Our work also highlights the necessity that sound science is essential in decision-making for the current and future public health pandemics,” said UC San Diego’s Nobel Laureate in chemistry and Distinguished Professor Mario Molina.
加州大学圣地亚哥分校的诺贝尔化学奖得主、著名教授Mario Molina说:“我们的工作还强调了这样一种必要性，即可靠的科学对于当前和未来的公共卫生大流行病的决策至关重要。”
The study shows that, between April 6 and May 9 in Italy and New York City mandated face coverings significantly reduced the number of infections by more than 140,000 between the two epicenters.
研究表明，4月6日至5月9日，意大利和纽约市强制使用口罩后，这两个中心的感染人数显著减少了14万。
The scientists quantified the effects of face-covering by projecting the number of infections based on the data before Italy and New York City implemented the use of face masks on April 6 and April 17, respectively (see Figure 2A). The inability of social distancing, quarantine and isolation alone to curb the spread of COVID-19 is also evident from the linearity of the infection curve prior to the onset of the face-covering rule in Italy and in New York City on those dates (see Figure 2 B and C).
科学家们根据意大利和纽约市分别于4月6日和4月17日开始使用口罩前的数据预测感染人数，从而量化了口罩的效果(见图2A)。在意大利和纽约市开始实行戴口罩之前，从感染曲线的线性也可以明显看出，仅靠社会距离和隔离无法遏制COVID-19的传播(见图2 B和C)。
The scientists also compared the numbers of daily new cases between New York City and the U.S. from March 1 to May 9 (Figure 3). The daily numbers of newly confirmed infections show a sharp increase in late March and early April. After April 3, the only difference in the regulatory measures between New York City and the U.S. lies in the city’s April 17 face-covering rule.
科学家们还比较了3月1日至5月9日纽约市和美国每天新增病例的数量(图3)。3月底至4月初，每天新增确诊病例的数量急剧增加。4月3日之后，纽约市和美国在监管规定上的唯一区别在于，纽约市4月17日出台了戴口罩的规定。
three graphs comparing 2020 pandemic trends between Wuhan, Italy, and NYC
三张图表比较了武汉、意大利和纽约在2020年的流行趋势
（图2。从武汉到意大利再到纽约。(A)武汉、意大利和纽约市2020年的趋势和缓解规定的比较。竖线表示实施缓解规定的日期。这两个黑色圆圈标记了戴口罩规定被实施的日期。黑色虚线表示在实施该规定之前，基于数据线性回归的不戴口罩情况的投影。(B)对在意大利实施戴口罩规定之前确认的感染人数进行线性回归。阴影的垂线表示在意大利北部实施戴口罩规定的日期。(C)纽约市实施戴口罩规定之前的确诊感染人数的线性回归数据。有阴影的垂直线表示纽约市实施戴口罩规定的日期。在B和C中，圆圈分别为报告值，虚线分别表示已确诊感染在戴口罩前后的拟合和投影。）
According to the researchers, the decreasing rate in the daily new infections in New York City with mandated face-covering sharply contrasts with the United States’ mask-free measures of social-distancing and shelter-in-place, further confirming the importance of face-covering in intervening the virus transmission.
根据研究人员的说法，在纽约市，强制戴口罩的每日新感染率的下降与美国的社交距离和住所的无口罩规定形成鲜明对比，进一步证实了口罩在干预病毒传播中的重要性。
“We conclude that the wearing of face masks in public corresponds to the most effective means to prevent inter-human transmission, and this inexpensive practice, in conjunction with simultaneous social distancing, quarantine and contact tracing, represents the most likely fighting opportunity to stop the COVID-19 pandemic,” said Renyi Zhang, distinguished professor of atmosphere science at Texas A&M.
“我们得出结论,在公共场合戴口罩是对应预防人类传播的最有效手段，且性价比高，同时结合社会距离、检疫和接触者追踪，是最有可能阻止COVID-19继续大流行的战斗机会,”RenyiZhang说，他是德州农工大学的杰出大气科学教授。
Molina agreed. “The unique function of face-covering to block atomization and inhalation of virus-bearing aerosols accounts for the significantly reduced infections in China, Italy and New York City , indicating that airborne transmission of COVID-19 represents the dominant route for infection,” stated Molina.
Molina同意该观点。Molina说:“在中国、意大利和纽约，口罩的独特功能可以阻止携带病毒的气溶胶的雾化和吸入，这是导致感染显著减少的原因，这表明空气传播COVID-19是主要的感染途径。”
There are several ways for viruses to be transmitted from person to person. Infected individuals produce microscopic, virus-bearing particles that spread when they cough, sneeze, breathe and talk. This viral shedding produces large droplets and small aerosols — suspensions of particles in the atmosphere — which disperse and stay in the air at differing rates and for various times. They also have characteristic deposition patterns along the human respiratory tract.
病毒在人与人之间传播有几种方式。受感染的人会产生微小的携带病毒的颗粒，在他们咳嗽、打喷嚏、呼吸和说话时传播。这种病毒的脱落会产生大液滴和小气溶胶——空气中的悬浮颗粒——它们会以不同的速度和不同的时间分散并停留在空气中。它们也有沿着人类呼吸道特征的沉积模式。
“With typical nasal breathing, inhalation of airborne viruses leads to direct and continuous deposition into the human respiratory tract. In particular, fine aerosols penetrate deeply into the respiratory tract and even reach other vital organs,” explained Molina, adding that viral shedding is dependent on the stages of infection and varies between symptomatic and asymptomatic carriers.
“在典型的鼻呼吸中，吸入空气传播的病毒会直接和连续地沉积到人的呼吸道。特别是，细微的气溶胶能深入呼吸道，甚至到达其他重要器官，”Molina解释说，并补充说，病毒的脱落取决于感染的阶段，并在有症状和无症状携带者之间有所不同。
Previous experimental and observational studies on inter-human transmission have shown that aerosols play a significant role in transmitting many respiratory viruses, including influenza virus, SARS-CoV-1 and Middle East Respiratory Syndrome coronavirus (MERS-CoV). For example, airborne coronavirus MERS-CoV exhibited a strong capability of surviving, but it decayed quickly. Recent experimental studies on the stability of SARS-CoV-2 show that it remains infectious for hours in aerosols and up to a few days on surfaces.
以往关于人与人之间传播的实验和观察研究表明，气溶胶在传播许多呼吸道病毒，包括流感病毒、SARS-CoV-1和中东呼吸综合征冠状病毒(MERS-CoV)方面发挥了重要作用。例如，空气传播的冠状病毒MERS-CoV表现出很强的生存能力，但腐烂速度很快。最近对SARS-CoV-2稳定性的实验研究表明，它在气溶胶中可以持续数小时，在物体表面上可以持续数天。
Molina, Zhang and their colleagues demonstrated the contribution of airborne transmission to the COVID-19 outbreak by comparing the pandemic’s trends and mitigation measures worldwide, and by considering the virus’ transmission routes (see Figure 3).
Molina、Zhang和他们的同事通过比较全球范围内的大流行趋势和缓解规定，并考虑病毒的传播途径，论证了空气传播对COVID-19疫情的贡献(见图3)。
The COVID-19 outbreak is significantly more pronounced than that of the 2002–2003 SARS epidemic, and the disease continues to spread at an alarming rate worldwide, despite extreme measures taken by many countries to constrain it. The enormous scope and magnitude of the COVID-19 outbreak reflect not only a highly contagious nature but also exceedingly efficient virus transmission. While the mechanisms to spread the virus remain uncertain, current epidemiological and experimental evidence implicates airborne transmission via aerosols as a potential route for spreading the disease.
COVID-19疫情比2002-2003年SARS疫情显著，尽管许多国家采取了极端规定遏制疫情，但疫情仍在全球以令人震惊的速度蔓延。COVID-19疫情的巨大范围和规模不仅反映了其高传染性，也反映了病毒的极其高效传播。虽然病毒的传播机制尚不确定，但目前的流行病学和实验证据表明，通过气溶胶的空气传播是该病的潜在传播途径。
COVID-19 is transmitted via droplets for airborne and contact transmission
COVID-19通过飞沫传播，通过空气传播和接触传播
（图3。COVID-19的传播。）
The scientists explain that several parameters likely influence the microorganism’s survival and delivery in air, including temperature, humidity, microbial resistance to external physical and biological stresses, and solar ultraviolet radiation. Transmission and infectivity of airborne viruses are also dependent on the size and number concentration of inhaled aerosols, which regulate the amount or dose and pattern for respiratory deposition.
科学家解释说，几个参数可能会影响微生物在空气中的生存和传递，包括温度、湿度、微生物对外部物理和生物胁迫的抵抗力，以及太阳紫外线辐射。通过空气传播的病毒的传播和传染性还取决于吸入的气溶胶的大小和浓度，后者调节呼吸沉积的数量或剂量和模式。
The novel coronavirus outbreak, which was declared a pandemic by the World Health Organization (WHO) on March 11, 2020, has infected more than eight million people and caused more than 400,000 fatalities to date. Intensive efforts are taking place globally to establish effective treatments and develop a vaccine for the disease, including efforts by several UC San Diego researchers.
世界卫生组织(WHO)于2020年3月11日宣布新冠病毒爆发为大流行，迄今已感染800多万人，造成40多万人死亡。全球正在加紧努力，以建立有效的治疗方法，并开发针对该疾病的疫苗，加州大学圣地亚哥分校(UC San Diego)的几名研究人员也在为之努力。
