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  • A new virus emerges and spreads like wildfire.

    有一種新型病毒出現, 且像野火般散播出去。

  • In order to contain it, researchers must first collect data about who's been infected.

    為了控制住疫情,研究員首先必須收集資料,了解受感染的是哪些人。

  • Two main viral testing techniques are critical: one tells you if you have the virus and the other shows if you've already had it.

    有兩種主要的病毒檢測技術非常重要:一種能判斷你目前身上是否有病毒,另一種則能顯示你是否曾經染上病毒。

  • So, how exactly do these tests work?

    這些檢測的原理到底是什麼?

  • PCR, or polymerase chain reaction testing, targets the virus's genetic material in the body and is used to diagnose someone who is currently infected.

    聚合酶連鎖反應 (PCR) 檢測針對病毒在人體內的遺傳物質,可用來診斷受測者目前是否受到感染。

  • Yet, this genetic material may be present in such imperceptible amounts that actually detecting it is difficult.

    但,這種遺傳物質的量可能非常微小,微小到很難偵測到。

  • This is where PCR comes in: it's widely used to amplify genetic information to large enough quantities that it can be readily observed.

    此時 PCR 就派上用場了:PCR 被廣泛應用在將遺傳資訊放大到可以很容易觀察到的程度。

  • To develop a PCR test for a never-before-seen virus, researchers first sequence its genetic material, or genome, and identify regions that are unique to that specific virus.

    若要針對前所未見的病毒來開發 PCR 檢測,研究員首先得要對該病毒的遺傳物質,即基因組,做定序,並且找出該病毒與其他病毒不同的區域。

  • PCR then targets these particular segments.

    接著,PCR 會把目標放在這些特定區域上。

  • A PCR test begins by collecting a sample: this can be blood for hepatitis viruses, feces for poliovirus, and samples from the nose or throat for coronaviruses.

    PCR 檢測一開始要先收集樣本:肝炎病毒可以用血液樣本,小兒麻痺病毒可以用糞便樣本,冠狀病毒可以用取自鼻子或喉嚨的樣本。

  • The sample is taken to a central laboratory where PCR is performed to test for the presence of the virus' genome.

    樣本會被送到中央實驗室,在那裡進行 PCR,來檢測是否有該病毒的基因組。

  • Genetic information can be encoded via DNA or RNA.

    可以透過 DNA 或 RNA 來做基因資訊的編碼。

  • HPV, for example, uses DNA, while SARS-CoV-2, the cause of COVID-19, uses RNA.

    舉例來說,人類乳突病毒用的是 DNA,而引起 2019 冠狀病毒的 SARS-CoV-2 則用 RNA。

  • Before running the PCR, the viral RNA, if present, must be reverse transcribed to make a strand of complementary DNA.

    在進行 PCR 之前,病毒的 RNA ——如果有的話—— 必須要經過反轉錄, 來製造一股互補 DNA。

  • Researchers then run the PCR.

    接著,研究員會進行 PCR。

  • If the virus is present in the sample, its unique regions of genetic code will be identified by complementary primers and copied by enzymes.

    如果樣本中有病毒,其獨特的遺傳編碼區域就會被互補的引子辨視出來,並被酵素複製。

  • One strand of DNA becomes hundreds of millions, which are detected using probes marked with fluorescent dye.

    一股 DNA 就會變成數億股,會被帶有螢光標記染料的探測器偵測到。

  • If the PCR machine senses fluorescence, the sample has tested positive for the virus, meaning the individual is infected.

    如果 PCR 機器感測到螢光染料,樣本對該病毒的檢測結果就是陽性,意即受測者受到感染。

  • Immunoassays, on the other hand, tap into the immune system's memory of the virus, showing if someone has previously been infected.

    另一方面,免疫分析檢測的是免疫系統對病毒的記憶,顯示受測者是否曾經被感染過。

  • They work by targeting virus-specific antibodies generated by the immune system during infection.

    原理是,受到感染時,免疫系統會針對不同病毒產生出不同抗體。

  • These are specialized classes of proteins that identify and fight foreign substances, like viruses.

    這類抗體是有專門功能的蛋白質,能夠辨視出、對抗外來物質,如病毒。

  • Immunoassays may detect IgG antibodies, the most abundant class, and IgM antibodies, the type that's first produced in response to a new infection.

    免疫分析可偵測到 IgG 抗體, 這類抗體是最充足的抗體,及 IgM 抗體,在因應新感染時最先產生出來的抗體。

  • The presence of IgM antibodies suggests a recent infection, but since it can take the body over a week to produce a detectable amount, they're unreliable in diagnosing current infections.

    若有發現 IgM 抗體, 就表示近期有受過感染,但因為身體至少要一週才能產生出偵測得到的抗體量,若想診斷目前是否有受到感染,這種方式並不可靠。

  • Meanwhile, IgG antibodies circulate for an extended period after infection; their presence usually indicates that someone was exposed and recovered.

    同時,在感染過後,IgG 抗體還會額外在體內循環一段時間;發現這種抗體通常是表示受測者曾經接觸病毒且已復原。

  • Before the immunoassay, health professionals draw blood from an individual.

    在進行免疫分析之前,健康專業人士會幫受測者抽血。

  • This sample then comes into contact with a portion of the virus of interest.

    接著讓血液樣本和一部分要檢測的目標病毒做接觸。

  • If the body has, in fact, been exposed to the virus in the past, the body's virus-specific antibodies will bind to it during the test.

    如果受測者過去曾經有接觸過這種病毒,在檢測時,體內針對這種病毒產生的抗體就會和病毒結合。

  • This reaction produces a change in color, indicating that the sample tested positive and that the individual has been exposed to the virus.

    這種反應會造成顏色改變, 表示樣本檢測的結果為陽性,也就是該受測者曾經接觸過病毒。

  • Immunoassays are especially important when it comes to retroactively diagnosing people who were infected but went untested.

    免疫分析特別重要的應用是:回溯診斷曾經受過感染卻沒有被檢測出來的人。

  • And there's exciting potential for those who have developed immunity to a virus: in some cases, their blood plasma could be used as treatment in people who are currently fighting it.

    如果有人已經有可以抵抗病毒的免疫力,那是很讓人振奮的:在某些情況下,可以把他們的血漿拿來治療還在和病毒奮戰的人。

  • PCR and immunoassays are always in the process of becoming more accurate and efficient.

    PCR 和免疫分析的準確度和效率一直都不斷在提升中。

  • For example, innovations in PCR have led to the use of self-contained testing devices that relay results within one hour.

    比如,在 PCR 的創新上,已經出現了獨立檢測裝置,可以在一小時內得到結果。

  • Digital PCR, which quantifies individual pieces of target DNA, shows promise in further boosting accuracy.

    數位 PCR 可以量化目標 DNA 的個別片段,未來有很好的前景, 能將正確率大大提升。

  • And although immunoassays are difficult to develop quickly, researchers in Singapore were able to create one for SARS-CoV-2 even before COVID-19 was declared a pandemic.

    雖然免疫分析的發展很難快得起來,但新加坡的研究員已經能夠針對新型冠狀病毒建造出免疫分析,且時間還是在宣佈新型冠狀病毒大流行之前。

  • These tests, along with the scientists who develop them and the health professionals who administer them, are absolutely essential.

    這些檢測—— 及開發它們的科學家,和管理測試的健康專業人士—— 都是非常重要的。

  • And when deployed early, they can save millions of lives.

    如果能及早拿來實際應用, 數百萬人可能會因此得救。

  • We know that our bodies produce virus-specific antibodies, but how?

    我們知道我們的身體會產生特定病毒的抗體,但是是怎麼產生的?

  • Learn more about your bodies defenses with this video, or find out how a very different medical test works with this one.

    透過這支影片學習更多關於你的身體防禦機制,或在這支影片學到非常特別的醫療檢查。

A new virus emerges and spreads like wildfire.

有一種新型病毒出現, 且像野火般散播出去。

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B2 中高級 中文 美國腔 病毒 檢測 抗體 受測 免疫 樣本

【TED-Ed】病毒檢測流程的奧秘 (How Do Virus Tests Actually Work? - Cella Wright)

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    Celine Chien   發佈於 2020 年 08 月 08 日
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