感染了SARS-CoV-2（可导致COVID-19的病毒）的人可以在说话，唱歌，咳嗽，打喷嚏甚至呼吸时传播病毒。 科学家认为口罩 帮助限制病毒传播 by protecting everyone else from the infected wearer.保护其他所有人免受感染者的侵害。 As a result, face maks are now mandatory in many cities, states and countries to limit the spread of COVID-19.结果，现在在许多城市，州和国家中，都必须强制使用面部按摩器以限制COVID-XNUMX的传播。
人们通常会戴外科手术，布或其他面罩，但不能完全防止病毒感染穿戴者 医用级口罩 do appear to offer more protection.确实提供了更多保护。 Nonetheless, these don't have the same level of protection as N95 or P2 “respirator” masks worn by many health-care workers.但是，它们的防护等级与许多医护人员所戴的NXNUMX或PXNUMX“呼吸器”面罩不同。 Additionally, how we wear the mask matters, as touching it often and not completely covering the nose and mouth renders it ineffective.此外，我们如何戴好口罩很重要，因为经常触摸口罩而不能完全覆盖鼻子和嘴巴会使口罩失效。
While these face coverings may not completely prevent us from getting infected with COVID-19, they probably reduce the number of virus particles we inhale — the “viral dose”.尽管这些面罩可能无法完全阻止我们感染COVID-XNUMX，但它们可能会减少我们吸入的病毒颗粒数量（“病毒剂量”）。 Scientists think a lower viral dose can reduce the severity of the disease we get.科学家认为，较低的病毒剂量可以降低我们所患疾病的严重程度。 Indeed, where universal face masking is implemented, a much higher proportion of确实，在实施通用面部遮罩的情况下， 新的COVID-19感染无症状.
Could this lower viral dose help us build some immunity to the disease?较低的病毒剂量可以帮助我们增强对这种疾病的免疫力吗？ Two researchers from the University of California have raised this possibility,加利福尼亚大学的两名研究人员提出了这种可能性， 在著名的《新英格兰医学杂志》上写作。 Although the theory hasn't been proven yet.尽管该理论尚未得到证实。
剂量使毒
How much virus we are initially infected with is a key determinant of how sick we get, according to evidence from other viruses and animal studies.根据其他病毒和动物研究的证据，我们最初感染多少病毒是决定我们患病程度的关键因素。 We also know this is true in hamsters that have been我们也知道这在曾经的仓鼠中是真的 实验性感染SARS-CoV-2.
Imagine if you touch a door handle that happens to have one virus particle on it, and then touch your nose and breathe that particle in. You will be infected with that one virus particle.想象一下，如果您触摸碰到上面正好有一个病毒颗粒的门把手，然后触摸您的鼻子并吸入该颗粒。您将被该病毒颗粒感染。 One一 评估, published in the Lancet, suggested one SARS-CoV-2 virus particle will have replicated to make nearly 30 new virus particles in 24 hours.在《柳叶刀》杂志上发表的文章暗示一种SARS-CoV-30病毒颗粒将被复制，在30小时内可产生近900种新的病毒颗粒。 Those 24 new particles can then go on to infect XNUMX more cells, giving rise to XNUMX new particles in the next XNUMX hours or so.然后，这XNUMX个新粒子可以继续感染另外XNUMX个细胞，在接下来的XNUMX小时左右会产生XNUMX个新粒子。
Now imagine someone sneezes right in your face and you inhale 1,000 virus particles.现在想象一下有人在您的脸上打喷嚏，您会吸入30,000个病毒颗粒。 After one round of replication you could have 900,000 particles, and then 1,000 in the round after.一轮复制后，您可能有XNUMX个粒子，然后在这一轮中有XNUMX个。 In the same period of time your body could be dealing with XNUMX times more virus, compared to the first scenario.与第一种情况相比，在同一时间段内，您的身体可能承受的病毒数量增加了XNUMX倍。
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不同类型的口罩如何工作以阻止飞沫说话，咳嗽和打喷嚏（胸部）。
Once the immune system detects the virus, it has to race to get it under control and stop it replicating.一旦免疫系统检测到病毒，它就必须进行竞争以使其受到控制并阻止其复制。 It does this in three main ways:它以三种主要方式执行此操作：
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告诉我们的细胞如何破坏病毒复制
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产生识别和中和病毒的抗体以阻止其感染更多细胞
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产生专门杀死病毒感染细胞的T细胞。
While the first step is relatively quick, creating specific antibodies and T cells takes days or even weeks.尽管第一步相对较快，但创建特异性抗体和T细胞需要几天甚至几周的时间。 Meanwhile, the virus is replicating over and over again.同时，该病毒一遍又一遍地复制。 So the initial dose of virus really determines how much of the body the virus has infected before the immune system kicks fully into gear.因此，病毒的初始剂量实际上决定了在免疫系统全面发挥作用之前，该病毒感染了多少身体。
长期免疫又如何呢？
The more virus there is, the bigger the immune response has to be to control it.病毒越多，控制它的免疫反应就越大。 And it's the immune response that actually causes the symptoms, like fever.真正引起症状（例如发烧）的是免疫反应。 In an asymptomatic infection, we think the immune system has probably managed to get the virus under control early on, so the immune response itself is possibly smaller, and so we won't see any symptoms.在无症状感染中，我们认为免疫系统可能已尽早控制了病毒，因此免疫反应本身可能较小，因此我们看不到任何症状。
We also think many cases of very severe COVID-19 might really be a result of the immune system overreacting.我们还认为，许多非常严重的COVID-XNUMX病例实际上可能是免疫系统反应过度的结果。 This is why the steroid treatment dexamethasone, which suppresses the immune response, shows promise in treating severe cases (这就是为什么抑制免疫反应的类固醇治疗地塞米松在重症患者中显示出前景的原因（但不是温和的).
After we clear an infection, we keep some immune cells around in case we get infected again.清除感染后，我们会保留一些免疫细胞，以防再次感染。 These are B cells, which produce antibodies specific to SARS-CoV-2, and T cells, which kill virus-infected cells.这些是B细胞，它们产生对SARS-CoV-2特异的抗体，而T细胞则杀死被病毒感染的细胞。 This is also the premise behind vaccination: we can trick the immune system into making those SARS-CoV-XNUMX specific cells without having been infected.这也是接种疫苗的前提：我们可以诱骗免疫系统制造那些SARS-CoV-XNUMX特异性细胞而无需感染。
Because face masks might allow a small number of virus particles through, wearers might be more likely to get asymptomatic infections.由于口罩可能会允许少量病毒颗粒通过，因此配戴者可能更容易出现无症状感染。 This might be enough to protect them from future infection with SARS-CoV-2.这可能足以保护他们免受SARS-CoV-XNUMX的未来感染。 So if we are in a situation where there is high community transmission, and we can't always maintain physical distance, wearing a face mask might be a factor that helps us in the long run.因此，如果我们处于社区传播频繁的情况下，并且无法始终保持身体距离，则戴上口罩可能是长期帮助我们的因素。
这是支持口罩的另一个论点
While this sounds promising, there's still a lot we don't understand.虽然这听起来很有希望，但仍有许多我们不了解的地方。 We don't know yet whether an asymptomatic infection would generate enough immunity to guard against future infection — or if this is even measurable.我们尚不知道无症状感染是否会产生足够的免疫力来预防将来的感染-甚至是否可以衡量。
Viral dose is likely to be just one factor among many that determines how sick someone gets with COVID-19.病毒剂量可能只是决定某人患COVID-19的病情的因素之一。 Other factors include age, sex, and other underlying conditions.其他因素包括年龄，性别和其他潜在状况。 Finally, even with asymptomatic infections, we don't know yet what the long term effects of COVID-19 are.最后，即使是无症状感染，我们仍不知道COVID-XNUMX的长期影响是什么。 It's best to avoid getting COVID-XNUMX altogether if possible.如果可能的话，最好避免完全获取COVID-XNUMX。
Nevertheless, this is yet another reason to keep wearing face masks.尽管如此，这是保持戴口罩的另一个原因。 As many cases of COVID-19 are asymptomatic, we could still be transmitting the virus even without symptoms.由于许多COVID-XNUMX病例无症状，即使没有症状，我们仍然可以传播病毒。 That's why wearing a mask is a responsible thing to do, even if we feel fine.这就是为什么即使我们感觉很好也要戴口罩的原因。
关于作者
Larisa Labzin，分子生物科学研究所研究员 昆士兰大学
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