A retrovirus is a kind of virus that stores its genes as RNA, not DNA. When it gets inside a cell, it does something most living things do not: it writes that RNA “backwards” into DNA, and that DNA can settle into the host’s own genes. That reverse step is why it is called retro-.

A retrovirus反轉錄病毒 is a kind of virus是一種病毒 that stores its genes as RNA, not DNA它把自己的基因儲存成RNA，而不是DNA。When it gets inside a cell當它進入細胞裡，it does something most living things do not它會做一件大多數生物不會做的事：it writes that RNA “backwards” into DNA把RNA「反過來」轉寫成DNA，and that DNA can settle into the host's own genes這段DNA還可能嵌入宿主自己的基因裡。That reverse step這個逆向的步驟 is why it is called retro-就是它被稱為retro-的原因。

HIV, the virus that causes AIDS, is a retrovirus. Some viruses linked to cancer are too.

HIV, the virus that causes AIDSHIV，也就是引發愛滋病的病毒 is a retrovirus就是一種反轉錄病毒。Some viruses linked to cancer一些跟癌症有關的病毒 are too也是反轉錄病毒。

The same trick that makes these viruses dangerous also makes them useful: scientists can take a weakened retrovirus and use it like a delivery truck to carry a helpful gene into a cell. That is why the word shows up both in grim health news and in genetic engineering.

The same trick that makes these viruses dangerous讓這些病毒危險的那個機制 also makes them useful同時也讓它們變得有用：scientists can take a weakened retrovirus科學家可以拿一個減毒過的反轉錄病毒 and use it like a delivery truck把它當成一輛運送貨車 to carry a helpful gene into a cell把有用的基因送進細胞裡。That is why這就是為什麼 the word shows up both in grim health news and in genetic engineering這個字會同時出現在令人擔憂的健康新聞和基因工程的討論裡。

Though actually, not every serious virus is a retrovirus — a cold virus is not. The “retro” is about the copying direction, not about being old-fashioned.

Though actually不過其實，not every serious virus is a retrovirus不是每種嚴重的病毒都是反轉錄病毒 — a cold virus is not——感冒病毒就不是。The “retro” is about the copying direction「retro」講的是複製的方向，not about being old-fashioned而不是指老派過時。