概论-病毒与宿主的博弈

地球上的病毒

Viruses on Earth

我们所在的地球，是一个组成复杂的地球，更是一个生气蓬勃的地球。在这颗美丽宏伟的星球上，除了我们人类，还存在有千姿百态的植物、形形色色的动物。而若我们将视野缩小、再缩小，我们会发现，其实还有数量巨大的、肉眼无法看到的微生物与我们共存，它们包括病毒、细菌、衣原体、寄生虫等。

The earth we live in is complex and vibrant. On this beautiful and magnificent planet, besides humans, there are also a variety of plants and animals. But if we zoom out, zoom out, zoom out, we find that there are actually a huge number of invisible microbes coexisting with us, including viruses, bacteria, parasites, and so on.

病毒是一种体积微小、结构简单、严格寄生于动植物细胞和细菌内的非细胞生物。美国作家卡尔·齐默曾写过一本名叫《病毒星球》的书，该书名是对地球一种准确的描述。在地球上，病毒无处不在，海洋、冰川、热泉、空气中都能有它们的身影。尤其是占地球表面积71%的海洋，这是病毒最主要的生境，海底沉积物中的病毒大约占到了地球病毒总数的87%。据研究，每升海水中的病毒颗粒数量可达1000亿，这比2022年全球人口数的12倍还要多。在地球的所有海水中，大约有10³¹个病毒颗粒。

A virus is a small, simple, strictly parasitic organism in either plant or animal cells or bacteria, and is a kind of non-cellular life form. American author Carl Zimmer has written a book named “A Planet of Viruses”, the title of which is an accurate description of Earth. Viruses are everywhere on Earth, in the oceans, glaciers, hot springs, the air. In particular, the ocean, which covers 71 percent of the Earth’s surface area, is the primary habitat for viruses, with about 87 percent of the planet’s viruses found in ocean floor sediments. According to research, there are up to 100 billion virus particles per liter of seawater, which is more than 12 times the number of people on the planet in 2022. In all of the ocean water on Earth, there are about 10³¹ virus particles.

病毒对地球产生了多方面影响，也就不难理解了。还是拿海洋病毒举例，病毒可直接影响海洋微生物的生化作用，从而改变海洋的微生物群落结构。据报道，全球病毒每年因裂解宿主细胞而释放的有机碳可达3.7-5*10⁷吨，这是异养微生物有机碳的重要来源。

It is not hard to understand how viruses affect the planet in many ways. Taking marine viruses as an example, viruses can directly affect the biochemical action of marine microorganisms and thus change the microbial community structure in the ocean. Worldwide, viruses have been reported to release 3.7*10⁷-5*10⁷ tons of organic carbon annually by lysis of host cells, which is an important source of organic carbon for heterogeneous microorganisms.

病毒之所以分布如此广泛，是因为它们对恶劣的环境有极强的抗性。近年来科学家发现一种病毒SIRV2，其宿主是一种名叫冰岛硫化叶菌的细菌，这种细菌生活在80摄氏度的酸性（PH≈3）热泉中。科学家通过电子显微镜，观察了使得该病毒具有抗热、抗旱和抗紫外线等抗性的结构特征，也正因为具独特结构有能产生上述抗性的独特结构，病毒才得以在如此极端的坏境中生存。

Viruses are so widely distributed because they are extremely resistant to harsh environments. In recent years, scientists have discovered a virus SIRV2, which is hosted by a bacteria called Sulfolobus islandicus, which lives in acidic (PH≈3) hydrothermal vents at 80 degrees Celsius. Using an electron microscope, the scientists looked at the virus’s resistance to heat, drought, and ultraviolet light, which allows it to survive in such extreme conditions.

病毒在宿主与环境中的状态

The state of the virus in the host and environment

不同病毒之间的“体型”差距比较大。最小的病毒只有几纳米，需要用电子显微镜才能看到。常见的球形病毒中，流感病毒粒径约80纳米，新型冠状病毒约125纳米，非洲猪瘟病毒约260纳米。而被称为“巨型病毒”的潘德拉病毒直径达1微米，用光学显微镜即可观察到。另外，由于最近一名11岁的法国男孩感染患病，一种叫“马赛病毒”的巨型病毒也出现在了人们的视野中。

The size difference between different viruses is quite large. The smallest virion is just a few nanometers long and can be seen only through an electron microscope. Among common spherical viruses, the diameter of the influenza virus is about 80 nm, the diameter of coronavirus SARS-CoV-2 is about 125 nm, and the diameter of African swine fever virus is about 260 nm. Pandoravirus, known as the ” Girus,” is one micron in diameter and can be seen with a normal microscope. As reported, Marseillevirus, an Girus, infected an 11-year-old French boy.

病毒与宿主的共进化-竞争关系

Co-evolution and competition relationship between virus and host

病毒与宿主的战争，是地球上持续时间最久的战争，它们与宿主共生存、共影响、共进化。无论是植物、动物还是人，都被迫参加了这场没有硝烟的战争、并往往受到伤害。病毒在人类历史上造成了多次的大瘟疫流行。HIV是一种“逆转录病毒”，其引发的免疫缺陷病（艾滋病）成为多少人的噩梦。该病毒会把遗传物质插入宿主细胞的DNA当中，当细胞分裂的时候将病毒自身的基因进行复制，不停传递下去，因此艾滋病是无法根除的。当然，病毒对人类与动物的影响不限于此，也不仅仅都是负面的。实际上，逆转录病毒家族在每个人的基因组中都保存了“基因遗迹”，这些核酸片段占到基因组DNA总量的8%；科学家发现一种内源性逆转录病毒能够合成合胞素，这是哺乳动物进化出胎盘的关键。

The war between viruses and their hosts is the longest-running war on Earth. They live with, influence, and evolve with their hosts. Plants, animals, and people have been forced to participate in this smokeless war, and have often been hurt. The virus has caused many of the great plagues in human history. A type of retrovirus that causes immunodeficiency (AIDS) has become a nightmare for many people. The virus inserts genetic material into the DNA of the host cell, and when the cell divides, the virus’s own genes are copied and passed on, so AIDS does not go to root. Of course, the effects of viruses on humans and animals are not limited to this, nor are they all negative. In fact, the retrovirus family is preserved in genetic remnants in everyone’s genome, with these nucleic acid fragments accounting for 8% of the genome’s total DNA. Scientists have discovered that an endogenous retrovirus can synthesize syncytin, the key to the evolution of placentas in mammals.

病毒的形态与结构

Morphology and structure of virus

刚才提到病毒大小差异很大，其实病毒的形态也是多样的，有球状、杆状和丝状、弹状、蝌蚪状。其中球形的病毒最为常见，这其中就包含我们所熟悉的新冠病毒。如果将如冠病毒从中间切开，可以看到病毒的结构是分层的，有点类似于俄罗斯套娃：最里层是遗传物质-核酸，最外层是囊膜；囊膜表面有30多个纤突蛋白，这些蛋白可不简单，经过多少亿年的进化，他们拥有了结合细胞膜受体的能力；病毒也因为有这些蛋白的存在而能稳稳地粘附在细胞上，这就是门锁-钥匙学说。

As mentioned earlier, viruses vary greatly in size, and viruses come in a variety of shapes, from spherical, rod, or filamentous, to bullet or tadpole shaped. Spherical viruses are the most common, including the familiar coronavirus. If you cut the coronavirus down the middle, you can see that the structure of the virus is layered, somewhat similar to a Russian doll. The innermost layer is the genetic material – nucleic acid, the outermost layer is the capsule; on the surface of the capsule are more than 30 fibrin proteins. These proteins are not simple. Over millions of years of evolution, they have developed the ability to bind to cell membrane receptors. This is the lock-key theory, and the virus sticks firmly to the cell.

病毒具有多形性特征。我们熟悉的流感病毒是实验室适应毒株、呈球形，由三部分组成：首先是位于内部的核心，包含遗传物质和复制酶；其次是构成病毒外骨架的基质蛋白M1及膜蛋白M2；最后是包裹在骨架外的一层磷脂双分子膜，膜上分布着两种重要的糖蛋白，即血凝素HA和神经氨酸酶NA。事实上，外界环境中长丝状的流感病毒比较常见。病毒粒子的形态是基因编码的结果，丝状有利于直接克服压力进入宿主细胞；病毒生存环境中的物理化学因素也会导致病毒形态的可逆性变化。

The virus is polymorphic. The familiar influenza virus is lab-adapted and spherical, but influenza viruses with long filaments are common in the environment. The morphology of virions is the result of genetic coding. Filamentous virions can directly overcome pressure and enter the host cell. The physical and chemical factors in the living environment of viruses can also lead to reversible changes in the form of viruses.

说到环境，天气因素对病毒的存活与传播有重要影响，尤其是温度和相对湿度。病毒在低湿度和高湿度条件下存活得更好，而在中等湿度（40-60%）条件下生存能力大大降低；高温对病毒的生存不利，低温则相对有利。也正是因为这一点，新冠疫情大流行时期很多国家非常关注的天气预报指数。应对不利的环境，病毒往往可以聚集形成“社会组织”，甚至形成“结晶体”，这可以被透射电镜捕捉到，保护大多数病毒粒子不被破坏，从而在严苛的环境中生存下去。病毒聚集与结晶可能是长期进化中的能力。

Viruses can be sensitive to their environment, and weather factors, especially temperature and relative humidity, play an important role in the survival and spread of viruses. The virus survives better under low and high humidity conditions, while its survival was greatly reduced under moderate humidity conditions (40-60%). High temperatures are bad for the survival of viruses, while low temperatures are relatively good. This is why many countries are paying close attention to the weather forecast during the COVID-19 pandemic. In response to adverse conditions, viruses can often gather to form a “social organization” or even form “crystals”, which can be captured by transmission electron microscopy. Such organization protects most of the virions from being destroyed and thus allows the virus to survive in a harsh environment. Viral aggregation and crystallization may be long-term evolutionary abilities.

我们一提到病毒就会联想到疾病，历史上人类对于疾病及致病源的认识也是循序渐进的。在我国古代，人们依据中华文明特色的“天人合一”整体观，结合生产和生活实践经验，认为动物体与环境之间以及动物体内各脏腑组织之间一般处于相对稳定状态，自然界气候反常会破坏这种稳定状态，导致动物发病。后来，人们注意到有毒气体（如瘴气、沼气、疠气）泛滥可以导致疫病、及其大规模流行。如葛洪等所著《肘后备急方》记载，东汉建武年间，士兵南阳击虏，感染了一种流行病，名“虏疮”，指出此（为）恶毒之气（所致）。这正是对天花病毒感染病例最早的记录。到了明代，吴有性在《瘟疫论》中将此类烈性传染病的病因归结于“天地之厉气”，而非气候反常，并指出“邪自口鼻而入”，特别强调了病原对于上呼吸道的侵入行为。

In Ancient China, it was thought that animal health and the environment were generally in a relatively balanced state, and that climatic abnormalities would destroy the balance, leading to animal disease. Later, it was thought that poisonous gases (miasmas or gas) can lead to large-scale epidemics. For example, Ge Hong et al. wrote “肘后备急方” records, during the Jianwu period of the Eastern Han Dynasty, that soldiers Nanyang Rupp were infected in an epidemic, named “Rupp虏疮,” and pointed out that it was caused by poisonous gas. This is the earliest recorded case of smallpox infection. In his “温疫论”, Wu youxing of the Ming Dynasty attributed the cause of such severe infectious diseases to “the severe gas of heaven and earth,” and pointed out that “the evil enters from the mouth and nose,” especially emphasizing the invasion of pathogens into the upper respiratory tract.

“比岁有病时行。仍发疮头面及身，须臾周匝，状如火疮，皆戴白浆，随决随生，不即治，剧者多死。治得瘥后，疮瘢紫黑，弥岁方减，此恶毒之气。世人云，永徽四年，此疮从西东流，遍于海中，煮葵菜，以蒜齑啖之，即止。初患急食之，少饭下菜亦得，以建武中于南阳击虏所得，仍呼为虏疮，诸医参详作治，用之有效方……”—《肘后备急方》。东晋葛洪原著名为《肘后方》，后经梁代陶弘景、金代杨用道分别增补后成书，为现存本。

“病疫之由，昔以为非其时有其气，春应温而反大寒，夏应热而反大凉，秋应凉而反大热，冬应因风雨阴晴，稍为损益，假令秋热必多晴，春寒因多雨，较之亦天地之常事，未必多疫也。伤寒与中暑，感天地之常气，疫者感天地之疠气，在岁有多寡；在方隅有浓薄；在四时有盛衰。此气之来，无论老少强弱，触之者即病。邪自口鼻而入，则其所客，内不在脏腑，外不在经络，舍于伏脊之内，去表不远，附近于胃，乃表里之分界，是为半表半里，即《针经》所谓横连膜原是也”—《瘟疫论》明·吴有性。

西方世界对于疾病的早期观点与中国相似，认为疾病是由有毒的空气（瘴气）导致的。随后，荷兰眼睛商人发明的显微镜，将细菌等微生物世界呈现在人们眼前时。直到1892年，俄国生物学家发现，感染的烟草叶提取液经未上釉的陶瓷滤器过滤后（除掉了细菌及杂质）仍能感染花草，这种滤过性病原只有在活细胞内才能生存复制，几年后被命名为病毒（virus, from Latin virus “poison, sap of plants, slimy liquid, a potent juice” ）。6年后（1898年）两位德国学者分离出第一种人畜共患病病原体——口蹄疫病毒。人类对于传染病病原的进一步探究，很大程度上依赖于研究手段的进一步发展。1931年，德国工程师发明了电子显微镜，推进了病毒化学时期的开始，并在1944年观察到烟草花叶病毒的杆状外形。1952年，美国长岛冷泉港的噬菌体小组的同位素标记实验证实DNA是噬菌体（病毒）遗传信息的载体。1953年，脊髓灰质病毒减毒活疫苗被成功研制出来。同年，沃森和克里克建立了DNA双螺旋结构理论，为病毒学进入分子病毒学时期奠定了基础。近现代组织和细胞培养技术的建立是病毒学发展史上的重大里程碑，促进了许多病毒学领域的重要发展。

The early view of disease in the Western world was similar to that in China, that disease was caused by toxic air (miasma). Later, the compound microscope, invented by Dutch spectacle maker, revealed the world of bacteria and other microorganisms. It wasn’t until 1892 that Russian biologists discovered that infected tobacco leaf extract filtered through unglazed ceramic filters (stripped of bacteria and impurities) could still infect plants and plants. The filtrating pathogen could only replicate inside living cells, and a few years later it was named a virus (from Latin virus “poison, sap of plants, slimy liquid, a potent juice”). Then two German scholars isolated the first zoonotic pathogen – foot and mouth disease virus. To a large extent, the further exploration of the pathogens of infectious diseases depends on the further development of modern research methods. In 1931, German engineers invented the electron microscope, ushering in the beginning of the viral chemistry period and observing the rod-shaped tobacco Mosaic virus in 1944. In 1952, the phage group at Cold Spring Harbor, Long Island, USA, confirmed that DNA was the carrier of genetic information of phages (viruses). In 1953, live attenuated spinal gray matter virus vaccine was successfully developed. In 1953, Watson and Crick established the theory of the double helix structure of DNA, which laid the foundation for virology to enter the period of molecular virology. The establishment of modern tissue and cell culture technology is a major milestone in the history of virology, and has contributed to many important discoveries in the field of virology.

病毒与地球上其它生物的生存与繁衍息息相关，我们每个人的日常生活其实都离不开“病毒”这个话题。

Viruses are closely related to the survival and reproduction of organisms on earth, and everyone’s daily life is affected by viruses.

除了造成人类的疾病与死亡，病毒同时还威胁着养殖业、宠物健康，以及人类生物安全，甚至能够左右人类历史的进程。

Except causing the diseases and deaths of humans, viruses also threaten the farming industry, pet health and human biosafety, and can even influence the history of mankind.

最著名的例子是，1918-1919年间，甲型流感病毒造成的大流行（即所谓“西班牙“大流感）感染人数就达10亿人，死亡人数超过4000万，是第一次世界大战死亡人数的4倍，它也成为了一战终止的重要原因之一。

The most famous example is that in 1918-19 alone, the Influenza A virus infected 1 billion people and killed more than 40 million — four times as many as in World War I — and it was one of the main reasons why the war ended.

狂犬病是一种人兽共患的急性传染病，死亡率近乎100%，潜伏期一般为2周-3个月、最长6年。要注意的是，狂犬病病毒可通过感染动物的唾液传播，发病动物舔舐口腔等粘膜，或者尚未愈合的伤口，都可以传播病毒。

Rabies is an acute zoonotic infectious disease with a mortality rate of nearly 100%. The incubation period is usually 2 weeks to 3 months and can be as much as 6 years. It should be noted that the rabies virus can be transmitted through the saliva of infected animals, or sick animals licking mucous membranes, (such as the mouth,) or open wounds.

禽流感可以经过呼吸道或密切接触，感染家禽、观赏鸟、水禽，以及候鸟，对人类也有威胁。2005年，H5N1型“禽流感”在东南亚爆发，肉鸡生长速度严重滞后、甚至成批死亡，给养殖户造成巨大的经济损失，同时还造成数百人被感染。

Avian influenza can infect poultry, ornamental birds, waterfowl, and migratory birds through respiratory or close contact. It is also a threat to humans. In 2005, the H5N1 “bird flu” outbreak in Southeast Asia severely delayed the growth of broiler chickens and even killed them off, causing huge economic losses to farmers and infecting hundreds of people.

蝙蝠被称为“病毒的储存器”，近年来多次出现在新闻头条。据报道，单峰骆驼接触到了带有病毒的蝙蝠，将病毒带到了中东地区，造成了中东呼吸综合征，病死率高达37.8%。蝙蝠也可以携带并传染埃博拉、马尔堡病毒，SARS病毒，亨德拉病毒、尼帕病毒等，通过我们身边的动物不时提出挑战，这种威胁并不遥远。

Known as a “reservoir” of viruses, bats have made headlines several times in recent years. Dromedary camels reportedly came into contact with bats carrying the MERS virus, bringing it to the Middle East and causing MERS, which has a case fatality rate of 37.8%. Bats can also carry and transmit Ebola virus, Marburg virus, SARS-CoV, Hendra virus, Nipah virus, and more, and the threat is not far away, with the animals around us always to be challenged from time to time.

接下来，我们将通过犬科、猫科、家禽、家畜等不同动物，走进病毒的世界，一起探索身边的动物病毒，深入了解病毒的形态与传播特点，思考病毒对动物和人类带来的种种影响。在这个春天，种下一颗科学的种子，让科学的萌芽在这片土地上茁壮成长。

Next, we will walk into the world of viruses through canines, felines, poultry, domestic animals and other animals, and explore animal virus to understand the form and transmission characteristics of viruses. We will think about the impacts of viruses on animals and humans. This spring, plant a seed of science, so that the bud of science in this country can thrive.

总编辑：牛立辰

文本：游婧玲、宫冉冉、王警、田文骏、张修忠（排名不分先后）

翻译：王晓佳

导演及编辑：牛立辰、雷逸雪、刘佳茵

解说：雷逸雪