为什么有些人的新冠感染症状会长期存在？

麦千叶

Nearly one in five people who have had COVID-19 in the United States continue to suffer from symptoms of long COVID. But why some people recover completely while others remain sick has been a mystery. Now research has provided some interesting clues.

A new study shows that bits of virus that survive in the gut（肠道） cause chronic inflammation， which reduces production of serotonin — a molecule critical for communication between nerve cells in the gut and brain. The authors of the new article suggest that waste of serotonin disrupts gut-to-brain communication， which can cause long-term neurological（神经系统的） symptoms such as “brain fog” and impaired memory.

The brain and the gut talk to each other. In fact， the gastrointestinal（胃肠的） nervous system with its own 500 million neurons is so large， it is sometimes called the “second brain.”

About 95 percent of the serotonin is produced in the gut， although the brain makes its own supply. Microbes that live in our gut also produce chemical neurotransmitters， including serotonin. While serotonin produced in the gut does not directly reach the brain， it can influence the brain via neuronal circuits through vagus nerve.

“Thats why when youre feeling stressed， you can get abdominal pain or diarrhea，” says Kenji Hashimoto， a neuroscientist at Chiba University in Japan.

This may explain how “long COVID might be linked through a pathway that originates in the gut and leads to serotonin reduction，” says Christoph Thaiss， a microbiologist at the University of Pennsylvania， who led the study.

“These are very important findings that help explain why serotonin levels remain low in certain long COVID patients following SARS-CoV-2 infection，” says Liam OMahony， an immunologist at APC Microbiome Ireland， University College Cork， who was not involved in Thaiss work.

（材料来自National Geographic网站，有删改）

1. According to the text， what makes some people suffer from long COVID？

A. The production of serotonin in the gut.

B. The production of serotonin in the brain.

C. The reduction of serotonin in the gut.

D. The reduction of serotonin in the brain.

2. What does the underlined word “impaired” in Paragraph 2 refer to？

A. Self-healed. B. Damaged.

C. Renewed.D. Strengthened.

3. According to Hashimoto， you can suffer from  under pressure.

A. abnormal painB. cell loss

C. toothacheD. diarrhea

4. Whats the attitude of experts mentioned in the text toward the new study？

A. Supportive. B. Disapproved.

C. Indifferent. D. Neutral.

1. C。解析：細节理解题。材料第二段中提到“在肠道中存活的少量病毒会导致慢性炎症，从而减少血清素的产生——血清素是一种对肠道和大脑神经细胞之间的交流至关重要的分子，血清素的消耗会破坏肠道与大脑的交流，从而导致长期的神经系统症状”。C项“肠道中血清素的减少”与原文相符，故选C。

2. B。解析：词义猜测题。材料第二段的第二句提到“血清素的消耗会破坏肠道与大脑的交流，从而导致长期的神经系统症状，如‘脑雾和记忆受损”。B项“被损坏的”与文意更为契合，故选B。

3. D。解析：细节理解题。材料第五段提到“这就是为什么当你感觉到压力时，你可能会腹痛或腹泻”，A项“反常的疼痛”与原文中的“腹痛”不符，B项“细胞消亡”和C项“牙痛”在原文中未有提及。D项“腹泻”与原文相符，故选D。

4. A。解析：推理判断题。综合材料最后三段的内容——“这就是为什么当你感觉到压力时，你可能会腹痛或腹泻”“这也许解释了为什么‘长新冠可能与一种通过起源于肠道并导致血清素减少的途径相关联”“这些非常重要的发现有助于解释为什么某些长期感染新型冠状病毒的患者血清素水平仍然很低”，我们可知三个专家对这项新研究都持赞同的态度。故选A。