这就是为什么许多病毒，如麻疹，只会使我们生病一次。
This is why many viruses, such as measles, make us ill only once.
它们可以产生足够多的新病毒来训练免疫系统杀死并记住它们，所以人们只需要接种一次疫苗。
They can produce enough new viruses to train the immune system to kill and remember them, so people only need to take the vaccine once.
当人们第一次在显微镜下看到冠状病毒时，他们发现它的刺突使它看起来像一个皇冠。
When people first saw a corona-virus under a microscope, they found that its spikes made it look like a crown.
虽然我们不能预言H5N1病毒何时或是否会引发一次大流行，但我们不能忽视一些警告性征兆。
While we cannot predict when or if the H5N1 virus might spark a pandemic, we cannot ignore the warning signs.
也是1979年以来，苏丹亚型埃博拉病毒第一次有报告的出现。
This was the first reported emergence of the Sudan Ebola virus since 1979.
亨德拉病毒在1994年澳大利亚21匹马暴发急性呼吸道疾病期间第一次得到确认。
Hendra virus was first recognized in 1994 during an outbreak of acute respiratory disease among 21 horses in Australia.
例如，一次预定的反病毒扫描可能弹出一个对话框来阻止正在测试的GUI。
For example, a scheduled anti-virus scan may pop up a dialog blocking the GUI you are testing.
当人们对流感病毒没有预先免疫性，他们就需要几周间隔的两次注射而不是一次注射-这在当时免疫接种很多人去保护他们操作是非常困难的。
When people have no pre-existing immunity to a flu virus, they need not just one but two doses of vaccine several weeks apart - making it very hard to immunise many people in time to protect them.
设在开罗的美国海军第三医学研究处5月10日进行的3次检测确认了该名儿童感染H5N1病毒。
Three tests conducted on 10 May by the Cairo-based US Naval Medical Research Unit 3 (NAMRU-3) confirmed the child’s infection with the H5N1 virus.
虽然这项研究并不是第一次测试抗癌病毒疗法，但这是第一次完整记录此类病毒在患者病变组织中的行为特征。
While the study is not the first to test a cancer-killing viral therapy, it is the first to thoroughly document the behavior of the virus in patients' biopsy tissue.
拜尔公司已经不是第一次把导致CCD的原因死死归结于诸如病毒、真菌或杀虫剂等非人为因素了。
This isn't the first time Bayer has mobilized an effort to pin CCD on a non-man made cause, such as a virus, fungus, or parasite.
这是西半球第一次发现该种病毒。
It was the first time the virus had been identified in the Western Hemisphere.
这是5年来印度首都第一次发现丙型小儿麻痹症病毒。
These are the first cases of P3 viral polio in five years in the Indian capital.
Evans认为VIRxSYS通过限制病毒单次感染而将这种可能减小。
Evans thinks Virxsys has made this less likely by limiting the vaccine virus to a single cycle of infection.
这些改进是一种永久的力量，无论h5n 1病毒是否引起下一次疾病大流行。
These improvements are a permanent strength, whether this H5N1 virus causes the next pandemic or not.
尽管延续几年的强化调查，但是研究未能发现该病毒的动物储主或确定两次暴发之间它隐藏在自然界的何处。
Despite intensive investigations extending over several years, research has failed to find an animal reservoir of the virus or determine where it hides in nature between outbreaks.
不过，这只是病毒的“第一次浪潮”——科学家们还不知道病毒是否会变得更危险。
However, this is the "first wave" of the virus - scientists don't yet know whether the virus will become more dangerous.
这可能是由于1977年的一次意外：当时前苏联偶然泄露了一株季节性H1N1流感病毒，此后这病毒便与通常流行的H3N2流感病毒株一起扩散开来。
We have this immunity because of a biological accident: in 1977, an H1N1 flu virus was accidentally released in the Soviet Union and has circulated ever since, alongside the regular H3N2 strains.
我们预期，也担心高度致死性H5N1禽流感病毒将触发下一次大流行。
We were expecting, and fearing, that the highly lethal H5N1 avian virus would spark the next pandemic.
当地社区渴望获得更多信息，要求举办关于艾滋病毒的更多讲座并要求在一次聚会上提供检测和咨询服务。
Hungry for more information, the local communities asked for more talks on HIV and for testing and counselling services to be provided at one of the meetings.
2009年流感大流行是艾滋病毒/艾滋病出现以来的第一次流感大流行。
The 2009 influenza pandemic is the first to occur since the emergence of HIV/AIDS.
新浪微博于今晚8点钟遭受了第一次大规模的病毒袭击。
Sina Weibo experienced its first mass virus attack at around 8pm this evening.
一旦病毒活动减弱，一次关键的沟通会议将有助于减轻出现下一波传染的可能性。
Once the level of disease activity drops, a critical communications task will be to balance this information with the possibility of another wave.
如果这不是神的旨意，那么可能是一次简单的进化，这个病毒出现并将人类暴露在了其毒手下。
If it wasn't an act of god, it could have been simple evolution. The virus could have occurred natural and people began to become exposed.
我们每三到四天查看一次培养物，并通过添加捐献者的淋巴细胞使感染病毒的细胞存活了三周。
We checked the culture every three to four days and managed to keep the virus-infected cells alive for three weeks by adding lymphocytes from donors.
显然，这种逆转录病毒基因填补了哺乳动物生物学的一个小生境，但是从另一方面来说，在第一次感染此类病毒以前，哺乳动物已经能够完美的生殖了。
Clearly, this retroviral gene fills an important niche in mammalian biology, but, on the other hand, mammals were able to reproduce perfectly well before they were first infected.
而其它一些新指南则使世界第一次有望看到一代无艾滋病毒婴儿的出生。
Other new guidelines give the world its first vision of a generation of babies born HIV-free.
而其它一些新指南则使世界第一次有望看到一代无艾滋病毒婴儿的出生。
Other new guidelines give the world its first vision of a generation of babies born HIV-free.
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