真菌会不会不断进化最后消灭人类？
The following article is from 廖博士全球健康快讯 Author 廖博士
Could a parasitic fungus evolve to control humans?
一只蚂蚁，不再控制自己的身体，爬离蚁群，危险地挂在树叶上，等待死亡，因为真菌吞噬了它的身体，从它的头部冒出，并向空气中释放孢子。An ant, no longer in control of its body, crawls away from its colony, hangs perilously on a leaf, and waits to die as a fungus consumes its body, emerges from its head, and releases spores into the air.
“它们就像森林里的这些可怕的小圣诞饰品，”中佛罗里达大学的真菌遗传学家伊恩·威尔说。“They’re like these grim little Christmas ornaments out in the forest,” says Ian Will, a fungal geneticist at the University of Central Florida.
如果这种寄生真菌能对我们做同样的事情呢？What if this parasitic fungus could do the same thing to us?
这是根据视频游戏《最后的我们》（the Last of Us）改编的新电视节目的故事来源。在该节目中，由于气候变化导致的气温升高，一种真菌席卷了世界，将人类变成了寄生虫控制的僵尸。That’s the premise of the new television show based on the video game The Last of Us in which, as a result of warming temperatures caused by climate change, a fungus takes over the world and turns humans into parasite-controlled zombies.
威尔说：“以一种幻想的方式，逻辑联系是存在的，但在现实生活中不太可能发生。”。尽管科学家们并不担心真菌会演变成僵尸，但气温升高确实会造成真菌感染恶化的风险。“In a fantastical way, the logical links are there, but it’s not likely to happen in real life,” says Will. But while scientists aren’t worried about fungi evolving to turn people into zombies, rising temperatures do pose a real risk of making fungal infections worse.
寄生虫如何感染蚂蚁？How does the parasite infect ants?
据报道，《最后的我们》（The Last of Us）的创作者尼尔·德鲁克曼（Neil Druckmann）受到了一段自然视频的启发，该视频显示了一种真菌，即单边蛇床草（Ophiocordychar夏草），感染了一只子弹蚁。冬虫夏草是一种广泛的昆虫寄生虫，也是一种流行的健康补充剂。但只有麦冬虫草能控制宿主的身体。Creator of The Last of Us Neil Druckmann was reportedly inspired by a nature video showing the fungus, Ophiocordyceps unilateralis, infecting a bullet ant. Cordyceps are a broad category of insect parasites, and a popular health supplement. But only ophiocordyceps control their host’s body.
纽约植物园的寄生真菌专家若昂·阿劳霍（João AraúJo）表示，已知大约35种麦冬虫草真菌会将昆虫变成僵尸，但可能有多达600种。About 35 of these ophiocordyceps fungi are known to turn insects into zombies, but as many as 600 may exist, says João Araújo, an expert on parasitic fungi at the New York Botanical Garden.
感染的最初迹象是不稳定和异常的行为。科学家认为，这种寄生虫通过在大脑周围生长真菌细胞来物理控制宿主，真菌细胞劫持昆虫的神经系统来控制其肌肉。目前尚不清楚它是如何做到这一点的。The first signs of infection are erratic and abnormal behavior. Scientists think the parasite takes physical control of its host by growing fungal cells around the brain that hijack an insect’s nervous system to control its muscles. It’s unclear exactly how it does this.
每一种制造僵尸的真菌物种都是为了与特定的昆虫相匹配而进化的，因此，除了它们进化来感染的细菌外，独特的菌株对生物体几乎没有影响。例如，一种在泰国进化为感染蚂蚁的虫草不能感染佛罗里达州的不同蚂蚁。Each zombie-creating fungus species evolved to match a specific insect, so unique strains have little effect on an organism except for the one they evolved to infect. For example, a cordyceps that evolved to infect an ant in Thailand can’t infect a different ant species in Florida.
威尔说：“如果从一种蚂蚁跳到人类身上很难，那绝对是科幻。”。“但这种认为温度在真菌感染中起作用的观点当然是合理的。” “If a jump from an ant species is hard, to jump to humans—that’s definitely sci-fi,” says Will. “But this idea that temperature plays a role in fungal infections is certainly reasonable.”
气温升高的威胁？A threat from rising temperatures?
即使没有寄生真菌的潜在威胁，也有很多其他真菌值得担忧。Even without a looming threat from parasitic fungi, there are plenty of other fungi to fear.
据估计，世界上有数百万种真菌，已知几百种对人类有害。保护我们免受严重真菌感染的一件事是我们自己温暖的身体。在98°F左右，人体温度过高，大多数真菌无法传播感染，他们更喜欢77°F至86°F的温度范围。There are millions of fungal species estimated to exist in the world, and a few hundred are known to be dangerous to humans. One thing that’s protected us from serious fungal infections are our own warm bodies. At around 98°F, human bodies are too hot for most fungal species to spread an infection—they prefer a range of 77°F to 86°F.
约翰斯·霍普金斯大学医学院的传染病专家Shmuel Shoham说：“我们之所以有皮肤真菌，原因之一是它们可以进入皮肤褶皱之间。这些地方是潮湿、黑暗的地方，真菌可以在比体温冷的地方繁殖。”。“One of the reasons why we have skin fungi is they can get between folds of skin. Those are sort of wet, dark places fungi can proliferate that are cooler than body temperature,” says Shmuel Shoham, an infectious diseases expert at Johns Hopkins University School of Medicine.
他说：“随着地球变暖，将使已经进化为能够承受更高室外温度的真菌更容易在人体内生存。“As the Earth warms up, that would make it easier for fungi that have evolved to withstand hotter outdoor temperatures to also be able to survive inside the human body.
科学家们认为，有一种真菌能够感染人类，这可能是由气温升高引起的，叫做耳念珠菌。There is one fungal species capable of infecting people that scientists think may have resulted from warming temperatures, called Candida auris.
直到2007年，科学界才知道它，但在2011年和2012年，它突然在三个不同的大陆上被发现。It wasn’t even known to science until 2007, but in 2011 and 2012, it was suddenly found on three different continents.
肖姆指出，当真菌进入血液时，其症状类似于细菌感染。对于免疫系统健康的人来说，击退它们通常不是问题。但许多人并不那么幸运：疾病控制中心估计，30%至60%的感染该真菌的患者已经死亡，尽管他们可能存在潜在的健康状况，因此很难确定耳念珠菌在其中发挥了多大的关键作用。When they enter the bloodstream, fungi present symptoms similar to a bacterial infection, Shoham notes. For people with healthy immune systems, fighting them off is typically not an issue. But many are not so lucky: The Centers for Disease Control estimates that 30 to 60 percent of patients infected with the fungus have died, although the possibility they had underlying health conditions makes it difficult to determine how pivotal a role Candida auris played.
但当被问及是否可能爆发类似新冠肺炎的真菌疫情时，卡萨德瓦尔表示，这并非不可能。But when asked if a fungal outbreak akin to COVID-19 was possible, Casadevall says it’s not out of the question.
Fruiting bodies erupt from a dead moth killed by the cordyceps fungus.
一只被虫草真菌杀死的死飞蛾身上长出了果实。
Photograph by Alex Hyde, Nature Picture Library
亚历克斯·海德摄，自然图片库