https://www.guokr.com/article/436763/
Spring decade ago, many of us have experienced the epidemic that swept the world, and the tragic consequences can remember. Today, SARS has over the past decade, but will not appear in the future one kind of appeal is stronger, broader prevalence of infectious diseases? If possible, it would have come from? Humans ready for it? Picture: Gary Ombler
(Text / David Quammen) In June 2008, Dutch • Yue Siteng Astrid (Astrid Joosten) and her husband left home, left for Uganda adventure travel. This is not the first time they go to Africa, but it has become the most should not go again.
41-year-old Yue Siteng electricity analyst, financial manager, she and her husband will travel to places outside of Europe every year. In 2002, they flew to Johannesburg, got off the plane fell in love with the land of Africa. The next few years, they have toured Mozambique, Zambia and Mali. In 2008, they go to the southwestern highlands of Uganda, the list of mountain gorillas in Seattle. Traveling day, the organizers provide a regional tour, go to Mo Lama dry Busen Lin (Maramagambo Forest), where there is a very well-known attractions, called the Serpent Cave (Python Cave). It is said that the cave entrenched African Rock Python, predation by bats grow into a monster.
Most of the tourists was not interested in snake holes, "but Yue Siteng and I always say, 'you have only one life, as much as possible try to do my son.'" Yue Siteng husband, Yap • Tall (Jaap Taal) told me later. So they went riding Busen Lin Mo Lama dry, and continue to walk about one mile, slowly climbing up, and finally came to a puddle next to a pond. Through moss and weeds, shadowy seen a crocodile eye generally low, dark hole. Yue Siteng and Tal together with another a tourist, follow the wizard climbed into this ominous cave.
Abnormal foot of the road difficult to walk: stones are everywhere, rugged, and easy to slip. The air is bad, filled with a sour fruit taste. Perhaps you can imagine a closed door, empty run-down bar, late at night after midnight, the earth is full of beer. The cave seems to have been eroded stream, or else there is the dark waterway. An already collapsed rock roof above the head, leaving a gravel ground, covered with coarse gravel, as is generally the lunar surface, and also to apply a thick layer of guano. Here it seems to be the fruit bats (Egypt Rousettus aegyptiacus at the perfect shelter) is. Egyptian fruit bats is a widely distributed in Africa and the Middle East Chiroptera, crow-sized, lot number. The cave dome densely covered with a thick layer of fruit bats, was disturbed by uninvited guests, to stir up unrest, pushing and shouting, many got off the cliff, scattered away, until you find a new space, only to re-settle down.
Yue Siteng and Tal have to look down the road, trying to maintain a balance, in order to avoid falling, ready to his hands. "I guess maybe that's why Yue Siteng infected with the virus," Tal told me, "I think that when she put his hands on a piece of rock covered with bat excrement by hand infected with a virus." Maybe after she hand touched the face, or lost pieces of candy into his mouth, "the specific reasons for this may be that she was infected."
Nobody forewarned dangerous Yue Siteng Tal Africa and the Batcave. They had never before heard of Marburg (Marburg). They only in the cave and spent about 10 minutes, saw a huge and slow boa constrictor, after left to continue their trip to Uganda, continue to visit the gorillas, boating and the line, and finally back to Amsterdam. Cave tours 13 days, has returned home Yue Siteng, he began to feel uncomfortable.
At first, the disease is not serious looks much better than the flu. After her temperature rose higher and higher. A few days later, organ failure began. Doctors know where the nearest Yue Siteng been to Africa, perhaps she suspected infection of Marburg hemorrhagic fever. "Marburg," Tal asked, "What is this?" Filamentous Marburg virus belongs to the virus family, it is of kin (including Ebola virus, including five kinds of virus) Ebola virus family. In 1967, a group of medical research with African monkeys were imported to West Germany Lahn River Marburg (Marburg an der Lahn), people first discovered the Marburg virus. These monkeys the virus to the laboratory staff, five people were killed. In the 10 years after this room, which have hundreds of Africans infected, the mortality rate as high as 90%.
The doctor Yue Siteng go to another hospital, were treated in isolation. She began rash, suffering from conjunctivitis, and began bleeding. The doctor uses a coma therapy, so that she can receive a stronger dose of antiviral drugs. Before she lost consciousness, Tal went into isolation wards, kissed his wife and said to her: "We are a few days later bye!" Hamburg laboratory testing of a blood sample Yue Siteng, and she was diagnosed Marburg virus. Yue Siteng's condition worsened, she stopped working organ, the brain began to hypoxia, cerebral edema soon appeared, and soon, Yue Siteng was declared brain dead.
The new emerging threats
To humans from wild animals broadcast new diseases are emerging. In many professionals view, is likely to occur in the future infectious disease caused by a new virus, they are all the time talking about it, consider it, the development scheme of maneuver to deal with it, they say - it any time soon. Photography: Brad Wilson
A horse died mysteriously in Australia, people around began to feel uncomfortable; the body of a chimpanzee on mainland Africa, the Ebola hemorrhagic fever passed villagers beggars; the end of a restaurant table on China Southern civet cats ( Paradoxurus hermaphroditus ), a new disease will be transmitted to the one diners, and soon the disease will spread to Hong Kong, Toronto, Hanoi and Singapore - it is SARS. These horrific examples are not isolated from each other, and are inextricably linked, and showed a trend: from wild animals to humans broadcast of new diseases are emerging.
Experts of these diseases called zoonoses, meaning can be extended from infected animals to infectious diseases between interpersonal. About more than 60% of human infectious diseases are all zoonoses. In most cases, these diseases by viruses, bacteria, fungi, native a biological, prions, and the six maggots caused by pathogens. Among them, was undoubtedly the most difficult viruses to their immense size, adaptability, and its ineffective antibiotic, antiviral drugs was only a few cases control. In all kinds of viruses, RNA viruses is undoubtedly the most irritating, SARS is a RNA virus that can spread directly between humans and animals caused.
Likewise, the claimed 50 million lives in the 1918 Spanish flu, which pathogen is an RNA virus, also belong to the summer of 2012 ravaged Uganda and other places of Ebola virus of this class. Marburg hemorrhagic fever, Lassa fever, West Nile disease, Nipah disease, dengue fever, rabies, yellow fever, SARS culprit, are all RNA viruses.
In the past six years, I have been asking virus researchers and government health officials of these two questions:
- The near future, will the emergence of a new type of highly infectious diseases, so that tens of millions of people died?
- If there is, then it would be like, come from?
For the first question, the answer from "maybe" to "very likely" to name a few. As for the second question, the answer to the discussion focused on zoonoses, particularly RNA viruses. In these professionals view, by the emergence of a new infectious disease caused by a virus, it can be said that the possibility of quite large. They talk about it all the time, to consider it, the development scheme of maneuver to deal with it. They say: it any time soon.
[The image above is slow to load, please be patient ...... Click image to see next] RNA viruses are widely distributed, highly adaptive, more easily than other types of pathogens, leading to large-scale epidemic diseases. Influenza virus is such a typical example, the above few pictures showing influenza virus invades a host cell, won control over breeding and propagation process.
- Step : Influenza virus via the respiratory system, invade the host body, and then by endocytosis, into the host cell, the virus split shell, the viral RNA fragments (the vRNA) and released into the cytoplasm RNA polymerase.
- Step Two : vRNA segments transcriptase and enters the nucleus, after image synthesis vRNA transcription enzyme fragment, messenger RNA (mRNA). It also generates a new copy of the vRNA segments.
- The third step : mRNA into the cytoplasm, with the transcription of ribosomal protein production. These proteins will be attached to the top of the cell membrane, or is more vRNA replicate in the nucleus.
- Fourth step : synthesis of new proteins and vRNA with the generated embedded in the cell membrane, the individual generates a new virus. By exocytosis, new viruses are released out individuals, ready to infect the next step.
Virus strategy
In order to understand how Yue Siteng victims, but also to cope with a large-scale epidemic under, need to understand how the virus evolved. • C • Edward Holmes (Edward C. Holmes), is the world's leading expert on the evolution of the virus. His job is to sit in empty office Center for Infectious Disease Dynamics at Pennsylvania State University and had a close look at the gene sequence of the virus, identify the virus evolution mode. Further particulars, as if he is reviewing the manic gorilla the keyboard, to generate a string of A, C, T, G and U (DNA or RNA molecules from 5 letters) lengthy sequences.
Holmes humorous, brought the virus in full flight, can write books in this area - he really wrote, published in 2009 by Oxford University's "evolution of RNA viruses and the emergence of" (The Evolution and Emergence of RNA Viruses ). "Most emerging pathogens are RNA viruses," he told me. Unlike viral RNA virus DNA, nor any other bacteria or pathogen.
Holmes said, RNA viruses too much, brings a great risk of infection. RNA viruses exist in seawater, soil, forests and cities, can infect bacteria, fungi, plants and animals. Each of eukaryotes on the planet are likely to have a corresponding RNA virus, and humans know little about. These viruses are highly adaptive, they constantly change themselves to adapt quickly to changing circumstances. Copy them fast, able to reproduce a huge number of communities in each host. Severe virus infection means that considerable spill - such as through sneezing, coughing, vomiting or bleeding, diarrhea, etc. - further accelerated the spread of the virus. Rapid reproduction rate and mutation probability of creating a diverse variants of RNA virus, given their strong ability to adapt to the new host environment.
Most DNA viruses will reflect the opposite characteristics. Their low infection rate, a smaller population. Stocks continued their policy more "tend to be hard work route", by the perseverance and guile. DNA viruses lurking, waiting to escape the patrol of the immune system and not override it on. They act low-key, only intrusion specific cell, a small amount of copy number, or simply the number remained stable. Varicella zoster virus, is a kind of typical DNA virus: initial onset, like chicken pox, like, after lurking for decades, like shingles as recurrence. DNA virus weakness is not well adapted to the new heterologous host. They are too stable, and narrow-minded and conservative, then work the old way convinced.
DNA viral genetic stability due to its molecular structure and replication: It is implemented using a DNA polymerase and a fit between the double-stranded replication. The enzyme RNA virus used, says a certain extent, the more "likely to make mistakes." Holmes said: "This is really a poor quality of the polymerase, it does not proofread nucleotide sequence, a mistake will not rework, why because gene sequences of RNA and DNA viruses compared to most simply too trivial? probably only in number hovered between 3000-30000. "If you want a more efficient synthesis of the polymerase, the need for more genetic information is encoded more of the base sequence. "
The nucleotide sequence of RNA Why so simple? Because they are self-replicating process is full of too many uncertainties. If the gene sequences carrying genetic information too, along with the accumulation of the replication process, the error will be more and more, and finally the whole virus individual can not work properly. In this case, there is an interesting statement: "Egan Paradox" (Manfred Eigen). • Manfred Eigen (Manfred Eigen) is a German chemist, Nobel Prize winner for self-replicating molecule has a unique study. He proposed this paradox describes a molecular size limit, the limit is exceeded, these molecules will be due to the high mutation rate and stop copying, demise. RNA viruses, and it was bound up, in order to overcome its weaknesses copy error-ridden, they had to win in number and highly contagious. Although we can not break Egan paradox, but they can find ways around it, but by virtue of the instability win. Replication errors brought a lot of variety, which makes them maintained a high rate of evolution.
"DNA virus genome can have huge," said Eddy. Unlike RNA viruses, DNA viruses from Egan paradox of restraint, even can absorb and integrate the DNA sequence of the host, to help confuse the host's immune system. Yourself long latent viral DNA in the host down, maintaining a low replication efficiency, spread themselves through some of the more secret methods, such as sexual transmission and mother to child transmission. "RNA viruses can not do that." They replication efficiency is really no way reduced, there is no way to expand the genome.
Lack of long-term security, not enough time nor enough adventure family property, but has a highly adaptable environment, if you are one such RNA viruses, would you do it? Along this line of thought, the answer is - among many different species of jumping around, that is, choose a variety of different host.
You, in helping the virus spread
Human-induced environmental stress and environmental collapse, is to provide more opportunities to spread from animals to humans to pathogens - today's technology and human behavior is at an unprecedented speed the spread of these pathogens. Picture: Gary Ombler
So, RNA viruses at what time choose to convert host it? Rodents transferred from one animal to the other rodents, from being transferred to the predator predators ...... such a conversion occurs frequently in the wild habitat, such as the silence of the forests, and there is no way in most cases, research and testing . However, at some point, this kind of jump between species when humans are turning from wild and domestic animals, we would perceive to.
We call this animal "reservoir hosts." It may be a monkey, a bat, or even a mouse. In the "reservoir hosts' body, the virus in a" truce "-like state, quietly habitat, does not result in any host of morbid symptoms. Virus moved from one host to another host phenomenon, called biologically "overflow" (Spillover). In the new host body, sometimes old truce no longer remain in force, the virus may become ferocious cruelty, violence. If the new host is a human, then this is a new zoonotic disease.
"Overflow" to humans, in terms of comparison with other viruses, it occurs more often in RNA virus body. They will be like following all sorts of infections from animals to humans: Lassa fever (first reported in 1969); Ebola haemorrhagic fever (1976); HIV-1 virus (drawn in 1981 to identify, 1983 in successfully separated), HIV-2 type (1986), evil Code (Sin Nombre, a non-famous Hantaan virus is a virus, 1993), Hendra virus (Hendra, 1994 years), avian influenza (1997 years), Xi Nipa virus (1998), West Nile virus (in 1999), SARS virus (2003), swine flu (2009). Marburg viruses are just another potential threat, although still rare nowadays, but for humans is fatal. Why are these such as the death knell of the virus "overflow" occurs constantly, and increasingly frequent it?
Deeper analysis of the problem: human-induced environmental stress and environmental collapse, is to provide more pathogens spread from animals to humans opportunities - of today's technology and human behavior is at an unprecedented speed the spread of these pathogens. Put another way, a new outbreak of animal diseases, and infectious diseases and old recurrence of the same, not just to bring human suffering, but also reflects the nature of what we are doing.
Earth population has reached 7 billion, and this number is rising, before reaching 9 billion, it seems that the trend of slowing growth will not occur. Many people live in large cities in densely populated. We continue to penetrate the human linger on those last virgin forests and ecosystems, the complete destruction of the physical structure and ecological linkages of these places.
We open up the Congo primeval forest road, opening the way in the Amazon rainforest, open up residence in Borneo, has even set up camp on the island of Madagascar. We tear down the towering trees, do not hesitate ruthless and resolute, we sell all kinds of hunting and wildlife, filling insatiable appetite. We settled in these places, creating one of the villages, factories, towns, extract resources, build new cities. We will domesticated animals brought here by livestock instead of wild herbivores. We have a large number of breeding livestock, like the large population of self as to establish large-scale farms, breeding hundreds of thousands of chickens, ducks, pigs, cattle, sheep and other domestic animals. We also across huge distances, fast import and export of livestock, livestock vaccinated against nature to antibiotics and other drugs. We also import and export of wild animals, as distinct from exotic pets. We import and export of animal fur, smuggling contraband of bushmeat, plants, many of which carries a large number of microorganisms and pathogens. We own to transport livestock faster than between cities, rapid travel between continents. We went to visit a monkey temple full of Asia, India's livestock market, the picturesque village of South America, New Mexico dusty monuments, Dutch cheese industry town, as well as the East African cave full of bats, Australia Racecourse - Breath the air every place, every place feeding of small animals, full of curiosity to four touch bumper, friendly locals and shake hands, then jump on a plane non-stop to the house. Human precisely to ambitious germs, crowds and provide more than enough as the host may be an individual.
In addition, ecological adaptation and evolution of physiological animal-borne diseases is worth the focus of consideration. The ecological environment to provide a large number of virus "overflow" opportunity. The evolution is to seize this opportunity to explore more opportunities, the "overflow" into infectious diseases. However, ecology and evolutionary physiology appears to belong to the category of science, and medical and public health services are far apart. If infectious diseases from wild animals to bring the world is so eye-catching threat, what can we do about it? Furthermore, RNA viruses everywhere Jie, but only a part of mankind to distinguish among very few. It can be separated out from the field environment, Tracking and confirm their host and viral systems studied even less. Only when the above-mentioned research work have been attended to, to be able to say, it is expected to develop appropriate vaccines and treatments to control this virus. This is the laboratory scientists - such as livestock ecologists, epidemiologists, virologists and laboratory chemist species play - areas where the struggle. If you try to understand the operation of the mechanism of animal diseases, it is necessary to find out the presence of these pathogens in the world, cultivating them in cell culture media old-fashioned way, carefully observe them, determine their gene sequences to identify them in the family tree It is located. In the major laboratories around the world, the work is in full swing. But to finalize it, it is very simple.
Infected range, can not be expected to
• Yue Siteng Esther Reed is not the only recently died of the Marburg virus in patients. In 2007, just a year before her trip to Uganda, almost in the same area, among the coal miners on a small scale outbreak of the epidemic. There were only four people affected by the infection and died. Where these workers are in a cave called Ji Kata southwest Uganda (Kitaka Cave) work.
After reports of people living in fear of this faded soon after, in August 2007, an international team to deal with Uganda, the Ugandan Ministry of Health to assist with the investigation. Members of the team include scientists Centers for Disease Control and Prevention (CDC) in Atlanta, scientists from the South African National Institute for Infectious Disease (NICD), as well as Geneva, World Health Organization (WHO) scientists. • Pierre Rollin (Pierre Rollin) from the CDC, is a filamentous virus and its clinical experts. At the same time, and he came along there from Atlanta • Jonathan Towner (Jonathan Towner), Brian • Oman (Brian Amman) • Carol and Serena (Serene Carroll). Pierre follow WHO early arrival, NICD • 斯瓦内普尔 Bob (Bob Swanepoel) • Kemp and Alan (Alan kemp) then came from Johannesburg. All of them are familiar with Ebola and Marburg hemorrhagic fever, and epidemic outbreak from a variety of responses, laboratory research and field research has accumulated a wealth of experience.
The roughly 100,000 Egyptian fruit bats live in the cave, it is the primary suspect Marburg virus hideout. Investigation team players, wearing chemical suits, rubber boots, safety goggles, gas masks, gloves and helmets by wearing only pants, T-shirt and slippers of local miners led, he came to the destination. The ground is still full of bird droppings, drooping hanging bat stir up in the miners expelled clapping sound, a sharp cry. These bats a huge head, every wingspan of about two feet (about 61 centimeters), when hundreds of thousands together passing the narrow tunnel toward you hit, really chilling. Before they realize it, a bat hit Oman's face, leaving a wound where the eyebrows. Towner also knocked a bit. Oman need to replant rabies vaccine, but more worrying is the risk of contracting Marburg virus. "This is a great place to infectious disease ah!" He exclaimed.
The cave has several roadway. Main lane almost eight feet high (about 2.5 meters). Due to the interference of mining activity, a lot of bat habitat to the transfer of the "Cobra roadway." Which boasts plenty of water and lots of bats as food, really good place for Cobra dwelling. Several miners led them to come to one filled with a tan warm water of the small room, and then left. Scientists down slowly along the brown pond, found a small stone chamber 3 bifurcation, every little roadway looked full of water at knee level. Carefully looked into the cave, they found more bats. The hole inside the high humidity, high temperature outside the hole than the 10 - 15 ℃. Slowly, their protective glasses are covered with a layer of fog. Respirators begin to absorb moisture, it increasingly difficult to breathe. They panting, sweating, feeling tied up in protective clothing in the quilt as bad as the garbage bag. They feel more and more "restless", Oman recalls, "We had to come out a cool down." This is just the beginning, but also so several times in the underground hiking Ji Taka.
A few days later, the team went to a desolate remote cave they dubbed "the cage" of. It is four mine workers infected before the onset of the place once worked. This time, NICD Oman, Vladimir door and lift • Alan Kemp has reached the deepest cave. The most narrow place, even only crawl crawling through the narrow gap off the cliff - as climbed into the garage door is not as dead. Here there are hundreds of different degrees of corruption only fruit bats corpse. What good sign begins to liquefy and saw piles of dead bats is not. This eliminates the fruit bats to some extent assumed the host as Marburg virus propagation. If a large number of fruit bats because the Marburg virus infection and death, the suspect untenable - perhaps the culprit is another bat, a rodent or ticks, spiders? These are all kinds of speculation requires further investigation and deliberation. For example, if the host is suspected tick words: Here you can have a countless ticks hiding in rock crevices and shelter bat, waiting for the chance to drink a mouthful of blood. These people continue to work hard at, they put the dead bats put into the bag, but also caught a few live, the same into his pocket. He followed the same route creeping back, struggling to drill the low slot. "It's too hard," Oman told me, "I never go to that awful place, if a stone rolled down, you're finished, completely trapped, mine rescue teams do not how the quality of Uganda kind."
At the end of this wild adventure, scientists collected about 800 bats. They dissected the bat, get a lot of blood and tissue samples. These samples were returned to Atlanta, Towner began to explore the ins and outs of Marburg virus in the laboratory. A year later, he published a paper, signed by authors Towner, Oman, Rollins and their colleagues worked with WHO and NICD. The paper announced that a number of important research results. They not only analyze the antibody and RNA sequences Marburg virus Marburg virus, but also to make research results have attracted worldwide attention - to find a live Marburg virus. In the CDC biochemistry at the security level (highest security level) 4 laboratory, pottery that Seoul and his colleagues from the body 5 bats, successfully isolated a viable copy of Marburg virus.
Further studies have shown that there are five types of Marburg virus, a different kind of gene sequences different. This shows that the Marburg virus in the body of a stranger with fruit bats, had a long history of evolution. These data together with sporadic RNA nucleotide sequence, fruit bats is confirmed Marburg reservoir hosts. In Ji Kata more than 100,000 bats, the team can determine, every night more than 5000 Marburg virus carried by bats fly out of the cave.
This is more than 5,000 bats are gone? It may be difficult to estimate the infected range. And this fruit bat populations in Ji Kata habitat, just around the numerous bat caves in the land of Africa, only a general.
Action and hope
Zoonotic diseases are not 100 victims without a benefit: they remind us that human beings and nature is a unified whole, can not be separated from each other. Photography: Brad Wilson
The risk of zoonotic disease caused by a real and serious, plus the risk of uncertainty. Experts tell us that there is no hope at predicted when a pandemic disease outbreak. The spread of infectious diseases, there are too many uncertainties. To try to predict in the macro, we need to establish a comprehensive detection of countless germs, which is unrealistic. Not so much closer to potential attempts, as it is far-fetched fantasy pride.
但是，现实中的困难并非意味着我们只能看着人畜共患病爆发迭起，毫无准备，束手就擒。最现实的防疫秘诀是，“基础进步，技术则进步”。这个“基础”指的是，充分理解什么样的病毒群落是值得去监测的，以及如何能在一种流行病在局部开始传播前、就在局部地区检测到它，如何在其转为大规模流行疾病前使其得到有效控制，如何尽可能在短时间内确定病原体的种属及其变种，尽快推出有效的预防疫苗和治疗方法或药物。如果实在没有办法对未来可能爆发的传染病进行有效预测，至少可以做到充分预警，使应对疫情的动作能够迅速及时，还可以在此基础上做到机动、可靠与全面。
已经做的诸如此类的努力已经相当可观。由世界卫生组织（WHO）疾病控制中心（CDC）等国际组织实施的雄心勃勃的各种计划，正在开始逐步实现中。这些计划的目标就是要全面辨识可能存在的病毒威胁。由于生物恐怖主义的潜在威胁，连美国国土安全局（DHS）与国防部高级研究计划署（DARPA）在内的众多国家安全部门也在努力参与其中，包括：WHO的世界卫生警报与防御网络（GOARN）、预言计划（DARPA实施），潜在大规模流行性疾病威胁预测计划（EPT），由美国国际开发署（USAID）实施；特殊病原体变种检测计划（SPB，由CDC实施）。这些名字看上去官话累牍的组织，实际上拥有着各领域刻苦勤奋的工作人员和紧急情况下能够迅速对病原体进行研究和检测的能力。此外，生态健康联盟（EcoHealth Alliance）之类的众多私人组织也加入到了研究队伍之中。
其中，有一家叫做全球病毒（Global Viral，GV）的组织工作非常引人瞩目。该组织的创始人内森•沃尔夫（Nathan Wolfe）获得了谷歌的资金支持，通过对遍布全球热带地区的探险者和狩猎者采集的血液样本进行分析，检测和预报大规模流行性疾病的发生。在哥伦比亚大学的梅尔曼大众卫生学院（Mailman School of Public Health），伊恩•利普金（Ian Lipkin）实验室的研究人员正在研发各种基因分子识别工具。既是生物学家也是同样优秀的物理学家的利普金，利用各种先进技术来筛查种类繁杂的病原体。这些技术包括：高通量测序（能够迅速且廉价地快速筛查大量DNA样本）、MassTag-PCR 技术（通过质谱分析法来筛查经过扩增的基因序列），以及 GreeneChip 基因芯片检测系统（能够在短时间内筛查数以千计的病原体）。生物学家在孟加拉的狐蝠以及在中国南方的小型蝙蝠采集到的血液样本，会被直接送往利普金那里。
这些科学家随时在保持警惕的状态之中。他们就仿佛哨兵，沿着边界巡逻，缉捕过境的病原体。下一次某些奇特的病毒将要从黑猩猩、蝙蝠、老鼠、鸭子，或是一只恒河猴身上传染给人类，或是将要开始在人际间传播，造成一群人感染致命疾病的时候，这些科学家会及时而迅速的发现它们，拉响防御的警报——希望他们能做到这一点。
在20世纪最初的几年，各大研究机构，包括洛克菲勒基金会下属的病理学家在内，无不建立起了野心勃勃的目标：彻彻底底地铲除传染病。他们在黄热病的研究上竭尽了力，耗费了多年的心血，花费了几百万美元的巨资，最后还是失败了。在对抗疟疾的研究上，他们同样失败了。然而，他们在对抗天花上却大获成功。为什么？
原因在于，这3种疾病间的差异相当繁杂：最为关键的就是天花既不会污染水源，也不存在帮助病菌传播的对应宿主：诸如蚊子、蜱虫等。简单来说：它的生态学特性相较简单，仅能在人类之间传播，所以比较容易去根除。1998年，世界卫生组织（WHO）发起了彻底消灭脊髓灰质炎的运动，由于情况与天花类似，这个目标是相当有希望达成的。然而，要根除人畜共患病，无论是埃博拉病毒之类的直接传染疾病，还是黄热病那样的通过昆虫传播的间接传染疾病，问题都要棘手得多。为了根除真正作为致病元凶病原体，难道要去消灭像蝙蝠、蚊子之类仅仅作为宿主的物种吗？这是不现实的，而且会招来巨大的舆论阻力。如果为了杜绝HIV新变种的突然出现，而去灭绝大猩猩，无疑更会引起大规模的激烈伦理争论。
说回来，人畜共患病也不是百害无一益的：它们提醒着我们，人类和大自然是一个统一的整体，彼此无法分割。事实上，所谓“自然界”并不存在，它只是一个人造的蹩脚的概念而已。这个世界上只有“世界”，人类只不过是其中的一部分，就像埃博拉病毒一样，就像流感病毒和HIV一样，就像马尔堡病毒和西尼罗病或SARS病毒一样，更别说黑猩猩、果子狸和非洲果蝠亦或是下一场灾难性传染病的病毒元凶，人类无甚区别。也许我们能做的，是尽可能将这些威胁阻挡在外，与之搏斗，充分预料可能会出现的最糟糕的灾难，做好尽可能全面的应对工作。可以做到这一切只需要一个理由：不管怎么说，与它们相比，我们还是要更聪明一些的。
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