The new coronavirus is the latest example of a disease that jumped from animals into humans. When infections do this they can be deadly — and COVID-19 is no exception.
Many viruses that jump into people, like MERS, seldom spread from person to person. They can still infect thousands, though; rabies (狂犬病) 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. COVID-19, by contrast, appears quite good at spreading from person to person. While we don’t know how deadly it is, Chris Coleman, a professor at the University of Nottingham, the UK, says, “It’s not the most deadly coronavirus we’ve ever had.”
To trace the new virus’s origins, researchers have been comparing its genome to that of other coronaviruses. This showed that it possibly derives from a strain that infects bats. “It’s highly related to bat coronaviruses,” says Vaithilingaraja Arumugaswami at the University of California, Los Angeles. This makes sense as bats are known to harbour many viruses, including coronaviruses. Viral infections are especially likely to spread among bats as they can fly long distances and roost close to each other. Bats also seem able to carry infections without getting ill, which helps spread the viruses.
The new coronavirus might have jumped from bats into another animal a few months or even a few decades ago, and then from that intermediate host into humans. We know that the coronavirus behind the SARS outbreak of 2002 to 2003 spread from bats into palm civets (狸猫) before infecting people.
Viruses that normally circulate among people can gradually become less lethal, 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.
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 ready in advance. This could mean creating vaccines that are effective against a wide range of viruses or vaccines that require only minor tweaks to work against a new viral strain, much like annual flu vaccines.
【小题1】What’s the second paragraph mainly about?| A．The intermediate host of viruses. | B．The mode of virus transmission. |
| C．The outbreak of the deadly COVID-19. | D．The serious consequence of COVID-19. |
| A．To support an idea. | B．To study virus infections. |
| C．To trace the coronavirus’s origins. | D．To map the new virus’s genome. |
| A．Complicated. | B．Active. | C．Healthy. | D．Deadly. |
| A．Seek right medicine for each virus. | B．Develop widely applicable vaccines. |
| C．Get away from animals carrying viruses. | D．Prevent viruses spreading among people. |
