一些溫和的病毒是否早已經侵入人體細胞？

01-15

如題，就是說，很久很久以前的一些病毒像溫和噬菌體侵入細菌一樣潛入人體而被遺留下來，到某個時候或者某個條件下被激活，造成人類滅絕？

Google一下JCV。這是一種傳染性很強的病毒，可以在下水道中存活，通過水源傳播。大約70%～90%的人都會攜帶這種病毒。

這種病毒會引起極度致命的進行性多灶性白質腦病。病人會在幾周到數月之內失去腦功能，失去運動，視覺，說話的能力。沒有藥物可以治療。

這麼可怕的疾病為什麼幾乎沒人聽說過呢？因為它只發生在極度免疫缺陷的人群中，通常是艾滋病人。

我覺得這個問題可以分成兩個部分來回答：

一、是不是可能會有病毒潛伏在人體里？

這個問題是肯定的，不僅僅是之前幾位知友所說的，人類基因組裡整合了不少病毒的基因；還包括隱形感染的病毒，因為相當多數量的病毒人類感染後是處於隱性感染狀態，即不引起臨床癥狀（產生這樣的情況原因很多就不細表了），比如柯薩奇病毒、埃可病毒、流行性乙型腦炎病毒等等，這些病毒，受感染者絕大數都是隱性感染。

二、在某些條件下病毒會激活，進而導致人類滅絕？

這些隱性感染的病毒是可能被激活的，一旦人體免疫力下降或者受到其它理化因素的影響，從而引發一些疾病。但是要滅絕全人類，我覺得任何一種病毒都很難辦到，因為可能要滿足傳染性強，致死率高，有一定潛伏期，無有效治療手段和疫苗，不易防控等許多條件，況且如果真是世界性的疾病，全球幾十億人，總會有些人天然免疫的人能存活下來的吧。

人類努力進化、與自然抗爭了幾十萬年，好不容易才成為自然界的霸主，哪有那麼容易就被滅絕啊，除非被人類自己！

理論上來說，進化的足夠好的病毒沒準可能一直寄生於人體而不產生病理性變化，沒準還能增強個人能力（這個是plague inc給我的腦洞）

但是這個問題的邏輯，你覺不覺得很像：

其實你房間里有一千隻變色龍，只是你沒看到而已？

你說的是溶源病毒（lysogen）吧

但是目前有個這樣子的問題

An important distinction here is that between the two decisions; lysogeny and lysis on infection, and continuing lysogeny or lysis from a prophage. The latter is determined solely by the activation of RecA in the SOS response of the cell, as detailed in the section on induction. The former will also be affected by this; a cell undergoing an SOS response will always be lysed, as no cI protein will be allowed to build up. However, the initial lytic/lysogenic decision on infection is also dependent on the cII and cIII proteins.

In cells with sufficient nutrients, protease activity is high, which breaks down cII.

[17]

This leads to the lytic lifestyle. In cells with limited nutrients, protease activity is low, making cII stable. This leads to the lysogenic lifestyle. cIII appears to stabilize cII, both directly and by acting as a competitive inhibitor to the relevant proteases. This means that a cell "in trouble", i.e. lacking in nutrients and in a more dormant state, is more likely to lysogenise. This would be selected for because the phage can now lie dormant in the bacterium until it falls on better times, and so the phage can create more copies of itself with the additional resources available and with the more likely proximity of further infectable cells.

A full biophysical model for lambda"s lysis-lysogeny decision remains to be developed. Computer modeling and simulation suggest that random processes during infection drive the selection of lysis or lysogeny within individual cells.

[18]

However, recent experiments suggest that physical differences among cells, that exist prior to infection, predetermine whether a cell will lyse or become a lysogen.

[19]

溶源周期和裂解周期的決定機制似乎還是不明晰的，但是從噬菌體的研究中我們知道，不管溶源周期要隔多久，總會發生裂解步驟，溶源到人類的系譜上的病毒……沒聽說過，別逗了

腦洞蠻大的

不然你以為線粒體是哪來的？