医学考博英语听力短文素材：新冠病毒进入人体会发生什么

　　2020医学博士英语新大纲听力题型有所变动，但做题方法和考点不变!重点练习长对话和短文!新大纲中减少了旧大纲中的短对话题，重点增加了长对话与短文两个部分的数量。其中，长对话部分由以前的1个对话，变成了三个相对较短的5个长对话，题也由原来的5题，增加至15题。听力内容方面：也不再仅限于有关医学方面的对话，而有可能增加通用题材的内容。短文听力方面，由原来的两个短文各5道题，增加至5篇医学科普短文，共15道题目。下面新东方在线考博频道为大家分享医学考博英语听力短文素材：新冠病毒进入人体会发生什么？。

Projecting (突起) from the envelope (包膜) are spikes of protein molecules. Both a typical influenza virus and the new coronavirus use their spikes (棘突) like a key to get inside a cell in your body, where it takes over its internal machinery, repurposing it to build the components of new viruses.

When an infected person talks, coughs or sneezes, droplets carrying the virus may land in your mouth or nose and then move into your lungs. Once inside your body, the virus comes into contact with cells in your throat, nose or lungs. One spike on the virus inserts into a receptor (受体) molecule on your healthy cell membrane (细胞膜) like a key in a lock. This action allows the virus to get inside your cell.

A typical flu virus would travel inside a sack made from your cell membrane to your cell’s nucleus that where your cell houses all its genetic material (遗传物质). The coronavirus, on the other hand, doesn’t need to enter the host cell (宿主细胞) nucleus. It can directly access parts of the host cell, called Ribosomes (核糖体). Ribosomes use genetic information (遗传信息)from the virus to make viral proteins, such as the spikes on the virus’ surface.

A packaging structure in your cell then carries the spikes in vesicles (囊泡), whichmerge with (融合) your cell's outer layer, the cell membrane. All the parts needed to create a new virus gather just beneath your cell's membrane. Then a new virus begins tobutt off (拼命工作) from the cell's membrane.

For this, we’ll have to look into your lungs. Each lung has separate sections, calledlobes (肺叶). Normally, as you breathe, air moves freely through your trachea(气管), or windpipe, then through large tubes, called bronchi (支气管), through smaller tubes, called bronchioles (细支气管), and finally into tiny sacs, called alveoli (肺泡). Your airways and alveoli are flexible and springy (有弹性的).

When you breathe in, each air sac inflates like a small balloon. And when you exhale, the sacs deflate. Small blood vessels, called capillaries (毛细血管), surround your alveoli. Oxygen from the air you breathe passes into your capillaries, then carbon dioxide (二氧化碳) from your body passes out of your capillaries into your alveoli so that your lungs can get rid of (去除) it when you exhale. Your airways catch most germs in the mucus (黏液) that lines your trachea, bronchi, and bronchioles. In a healthy body, hair-like cilia (纤毛) lining (覆盖) the tubes constantly push the mucus and germs out of your airways, where you may expel (排出) them by coughing.

Normally, cells of your immune system (免疫系统) attack viruses and germs that make it past your mucus and cilia and enter your alveoli. However, if your immune system is weakened like in the case of a coronavirus infection, the virus can overwhelm (使…难以承受) your immune cells and your bronchioles and alveoli become inflamed (发炎), your immune system attacks the multiplying viruses (不断增加的病毒). The inflammation can cause your alveoli to fill with fluid, making it difficult for your body to get the oxygen it needs. You could develop lobar pneumonia (大叶性肺炎), where one lobe of your lungs is affected, or you could have bronchopneumonia (支气管肺炎) that affects many areas of both lungs.

Pneumonia may cause difficulty breathing, chest pain, coughing, fever, and chills (寒战), confusion (意识模糊), headache, muscle pain, and fatigue. It can also lead to moreserious complications (严重并发症): respiratory failure (呼吸衰竭) occurs when your breathing becomes so difficult that you need a machine called a ventilator (呼吸机) to help you breathe. These are the machines that save lives and medical device companies currently ramp up (加快) production for. Whether you would develop these symptoms depends on a lot of factors, such as your age and whether you already have an existing condition (基础疾病).

While all this all sounds scary, the push to develop a coronavirus vaccine is moving at high speed. Studies of other coronaviruses lead most researchers to assume that people who have recovered from a SARS-CoV-2 infection could be protected from reinfection for a period of time. But that assumption needs to be backed by empirical evidence (科学证据) and some studies suggest otherwise.

There are several different approaches for a potential vaccine against the coronavirus. The basic idea is that you would get a shot that contains faint versions of the virus. The vaccine would expose your body to the virus that is too weak to cause infection but just strong enough to stimulate (刺激)an immune response. Within a few weeks, cells in your immune system would make markers called antibodies (抗体), which would be specific for only the coronavirus or specifically its spike protein (棘突蛋白).

Antibodies then attach to the virus and prevent it from attaching to your cells. Your immune system then responds to signals from the antibodies by consuming and destroying the clumps of viruses. If you then catch the real virus at a later stage, your body would recognize and destroy it. In other words, your immune system is now primed (提前准备，准备就绪).

Collecting evidence on whether this will be possible, safe and effective is part of what’s taking researchers so long to develop a vaccine. It is a race against time to develop a vaccine amid a pandemic (大流行病). Each step in vaccine development usually takes months if not years. An Ebola vaccine broke records by being ready in five years. The hope here is to develop one for the new coronavirus in a record-breaking 12 to 18 months. While all this will take time, stay home if you can to protect the most vulnerable and don’t forget to wash your hands for at least 20 seconds and as often as possible.

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