C

Infections that cross over from other species are a deadly problem. The new coronavirus(冠状病毒) is the latest example of a disease that jumped from animals into humans. When infections do this, they can be deadly-and 2019-nCoV is no exception.

Nearly all viruses and bacteria that infect other organisms are completely harmless to people. But a tiny proportion can infect us and cause so-called zoonotic diseases, which come from animals rather than people. Such diseases are a massive problem. They make around 2.5 billion people ill every year and kill 2.7 million. Not all zoonotic diseases cause serious illness, but the Ebola virus, for example, currently kills most of those it infects.

One reason zoonotic viruses can be this deadly is that we lack pre-existing immunity(免疫) to them. Another is that these viruses aren't adapted to humans. Viruses that normally circulate among people can develop to become less deadly, as this helps them spread. "They don't want you to drop dead within a day because you won't pass it to anyone else," says Chris Coleman at the University of Nottingham, UK.

To get infected, people need to come into contact with the animal the virus usually infects. This is most likely with domesticated animals. Camels carry the MERS coronavirus that causes sporadic human cases, for instance.

Many viruses that jump into people, like MERS, seldom spread from person to person. They can still infect thousands, though: rabies is mostly passed on by dog bites, but kills 60,000 people a year. Others, such as Ebola, can spread from person to person, but aren't very good at it and so cause relatively small outbreaks. The 2019 coronavirus, by contrast, appears quite good at spreading from person to person. We don't know how deadly it is yet.

Biologists have been warning for decades about the risks of animal viruses spreading to people. There is good reason to worry. The last global pandemic(传染病), the 2009 flu that killed up to 400,000 people, was caused by a strain of flu that came from pigs. And that flu is thought to be a descendant of the 1918 flu, which came from birds. HIV, which has infected about 75 million people, is now thought of as a human virus. But it jumped from chimpanzees into humans relatively recently, in the 1930s.

Coleman thinks there is little we can do to stop people coming into contact with animals that may carry dangerous viruses. "It's very difficult to control that," he says. Instead, he says we need to have vaccines( 疫 苗 ) ready in advance. This could mean creating vaccines that are effective against a wide range of viruses and developing vaccines that require only minor changes to work against a new viral strain, much like annual flu vaccines.

1. What does the underlined word "circulate" in Pra.3 probably mean?

A. Pass on. B. Attack each other. C. Die away. D. Work together.

1. What can we learn from the passage?
   1. People must keep away from wild animals.
   2. The majority of viruses are a massive problem.
   3. The 2009 flu had no connection with the 1918 flu.
   4. Vaccines are an effective option to fight against viruses.
2. The passage mainly aims to .
   1. analyze the origins of viruses
   2. explain the consequence of diseases
   3. draw people's attention to zoonotic viruses
   4. persuade people to protect the wild animals
3. Which of the following can be the best title for the passage?
   1. How Are Vaccines Made?
   2. Viruses Infected from Animals
   3. A Global Health Emergency
   4. Why Isn't There a Coronavirus Vaccine Yet?

D

How many more people can we squeeze onto our fragile planet? Surely, the Earth must be full? Pretending that human numbers can grow forever, with no ill-effects, is at best innocent and at worst utterly irresponsible.

Biodiversity loss, climate change, pollution, deforestation, water and food shortages - these are all worsened by our huge and ever-increasing numbers. Yet governments and most environmental groups choose to sidestep this giant elephant in the room. The human population was just 2.6 billion in 1950. But it has been 7.7 billion today and according to the UN it will reach 9.7 billion by 2050 and 11.2 billion by the end of the century. Where will so many people live? How will we feed them?

Unless we diffuse this "population bomb", by the end of the century we will need several Earths to survive. But we can't have several Earths, and so we will face a future of increasing poverty, food shortages, conflict and environmental degradation.

Admittedly, not everyone agrees with the UN's predictions. But even the doubters calculate that the human population will grow to 8 or 9 billion sometime between 2040 and 2060. Ultimately, there has to be a limit.

The good news is that the human populations of about two dozen countries, from Poland and Italy to Cuba and Japan, are now decreasing. But that's not true of most countries. The cradle of overpopulation is in Africa, which is where more than half of global population growth is expected to occur: from 1.3 billion people in 2020 to 4.3 billion in 2100.

The solution isn't rocket science. There are two drivers of population growth: birth rates and longevity. We all aim to grow old, after all, but we can reduce birth rates. That's not to say that anyone should be denied the right to have many children as they like. But it's a fact that wherever women are empowered and literated, have help with family planning and have access to medical care, they generally choose to have fewer children. And the birth rate falls.

So why the stony silence? Why such a failure of leadership from governments and environmental groups? I think it's for two reasons. First, calls for population control are often believed racist: relatively rich people in the developed world blaming poor people in the developing world. Second, it is often thought insincere. The problem is as much about consumerism as it is about population growth: westerners are consuming more and more, so it appears as if they are blaming the poor for the excesses of the rich. Most population growth is, indeed, taking place among those who consume almost nothing. But the uncomfortable truth is that we all need to consume much less.

Whatever the complications, we urgently need a UN Framework Convention on Population, just as we have for climate change. Either we limit our population growth or the natural world will do it for us.

1. What are the first three paragraphs mainly about?
   1. Environmental degradation made by humans.
   2. The increasing poverty coming with illnesses.
   3. The problems resulting from the growing population.
   4. Water shortages caused by climate change and pollution.
2. How do governments react to human population?
   1. They are too busy with other problems to solve it.
   2. They avoid seeking solutions to reduce population.
   3. They know the consequence and face the problem.
   4. They think the population will decline in the future.
3. What is practical for birth control according to the passage?
   1. Consuming much less than before.
   2. Removing the right to have more children.
   3. Decreasing population in developed areas.
   4. Educating women and providing health care.
4. What is the author's attitude to the ever-increasing human population?

A. Neutral. B. Concerned.

C. Skeptical. D. Indifferent.