科學家們試圖弄清楚夏季是否會減緩COVID-19的傳播

科學家們試圖弄清楚夏季是否會減緩COVID-19的傳播

The worst outbreaks of COVID-19 so far have been in colder parts of the Northern Hemisphere during winter or early spring. Will warmer weather slow the transmission?

到目前為止,在冬季或早春時,北半球的較冷部分地區(qū)發(fā)生了最嚴重的COVID-19疫情。天氣會減緩傳播速度嗎?

Could the Southern Hemisphere see outbreaks intensify as that part of the globe moves into winter?

隨著南半球進入冬季，疫情會加劇嗎?

And is it possible that transmission might be naturally interrupted as it is each year for the seasonal flu?

是否有可能像每年季節(jié)性流感那樣自然地中斷傳播?

These are some of the key questions about COVID-19 that scientists are trying to answer.

這些是科學家們試圖回答的關于COVID-19的一些關鍵問題。

"The seasonality of flu and other respiratory viruses has been known for hundreds of years, if not thousands," says Akiko Iwasaki, a professor of immunobiology at the Yale University School of Medicine. "During the winter months we tend to have a surge in the cases of respiratory infection, including the influenza viruses."

耶魯大學醫(yī)學院免疫生物學教授巖崎昭子說:“流感和其他呼吸道病毒的季節(jié)性即使不是幾千年，也有幾百年的歷史了。”“在冬季，包括流感病毒在內的呼吸道感染病例往往會激增。”

There are a number of factors that contribute to why the flu arrives in the winter but Iwasaki says the primary factor is the relative humidity of the air. In winter the drop in the amount of water vapor in the cold dry air makes it easier for viruses to become airborne.

造成冬季流感的原因有很多，但巖崎說最主要的因素是空氣的相對濕度。在冬天，寒冷干燥的空氣中水蒸氣含量的下降使得病毒更容易通過空氣傳播。

This makes what Iwasaki calls the "perfect setting" for respiratory viruses to transmit.

這就是巖崎所說的呼吸道病毒傳播的“完美環(huán)境”。

"When you cough or sneeze or even talk, you're generating these droplets that are coming out of your mouth," she says. "And some of them, if you're infected, will contain virus particles.

她說:“當你咳嗽、打噴嚏甚至說話的時候，你的口腔里就會產(chǎn)生這些飛沫。”“如果你被感染了，其中一些會含有病毒顆粒。

In very arid conditions, those particles lose the water vapor and they become airborne." This allows the virus to persist in the air for a long time, much longer than in summer.

在非常干旱的條件下，這些顆粒會失去水蒸氣，飄在空中。”這使得病毒可以在空氣中存活很長時間，比夏天長得多。

"This novel coronavirus is a cousin of the coronaviruses that are circulating in humans and just causing the common cold," she says. "So the property of the virus is likely to be similar to the common cold version of the coronavirus. So I would expect that this [new] coronavirus can also stay in the air better at lower relative humidity, meaning the indoor conditions that you find in the winter months." Meaning that it would be more likely to spread in winter.

她說：“這種新型冠狀病毒是在人體內傳播的冠狀病毒的近親，只會引起普通感冒。”因此，這種病毒的特性很可能與普通的感冒病毒相似。因此，我預計這種新型冠狀病毒在相對濕度較低的情況下也能更好地留在空氣中，這意味著它更有可能在冬季傳播。

The World Health Organization and the U.S. Centers for Disease Control and Prevention in their guidance on SARS-CoV2 downplay airborne spread, saying instead that the primary form of transmission is by "large respiratory droplets."This debate – airborne vs. droplets — is a crucial divergence in thought when it comes to figuring out if COVID-19 is going to be seasonal. If the primary form of transmission is airborne, then the novel coronavirus could become a seasonal disease. If it mainly spreads through "large respiratory droplets" then seasonality is less likely.

世界衛(wèi)生組織和美國疾病控制與預防中心在關于SARS-CoV2的指導意見中淡化了空氣傳播的重要性，稱主要的傳播形式是通過“大的呼吸液滴”。關于COVID-19是否會隨季節(jié)變化，這場爭論—空氣傳播還是液滴傳播，是一個重要的思想分歧。如果傳播的主要形式是空氣傳播，那么這種新型冠狀病毒可能成為一種季節(jié)性疾病。如果它主要通過“大的呼吸液滴”傳播，那么就不太可能是季節(jié)性疾病。

The transmission through "large respiratory droplets" works this way. When an infected person sneezes or coughs, virus-laden spittle flies out into the air. The particles, which may even be big enough to see, don't go very far: WHO estimates they travel about 3 feet before dropping onto surfaces directly around the infected person.

通過“大呼吸液滴”的傳播是這樣的。當感染者打噴嚏或咳嗽時，攜帶病毒的唾沫會飛到空中。這些顆粒甚至可能大到可以看到，但不會飛得太遠:世衛(wèi)組織估計，它們在直接落到感染者周圍的表面之前，會飛行約3英尺。

According to this model, if a person with COVID-19 is eating in at restaurant, they're far more likely to infect someone at their table than someone across the room.

根據(jù)這個模型，如果一個患COVID-19的人在餐館吃飯，他傳染給同桌的人的可能性比傳染給房間另一頭的人的可能性要大得多。

So if the new coronavirus primarily spreads this way on large droplets, seasonality may not matter.

因此，如果新的冠狀病毒主要通過大液滴傳播，那么季節(jié)性可能就不重要了。

Ben Cowling, an epidemiologist at the University of Hong Kong, also says warm temperatures haven't seemed to have stopped the spread of this virus.

香港大學的流行病學家本·考林也表示，溫暖的氣溫似乎并沒有阻止這種病毒的傳播。

Even in the U.S. southern states like Florida and Louisiana have been hard-hit along with colder states like New York and Michigan.

甚至在美國，南部的佛羅里達州和路易斯安那州以及較冷的紐約州和密歇根州也受到了嚴重的打擊。

But the worst outbreaks so far globally have been in cooler locations. So as the Southern Hemisphere moves into winter, researchers will be watching closely whether transmission of SARS-CoV2 increases in South America, Africa and Oceana as the temperature drops.

但到目前為止，全球最嚴重的疫情發(fā)生在溫度較低的地區(qū)。因此，隨著南半球進入冬季，研究人員將密切關注南美、非洲和大洋洲的SARS-CoV2傳播是否會隨著氣溫下降而增加。