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为什么有些感冒总不见好?

更新时间:2014-4-16 13:52:41 来源:华尔街日报中文网 作者:佚名

Sick Again? Why Some Colds Won't Go Away
为什么有些感冒总不见好?

About a month ago Sharon Gilbert was hit with a runny nose, sore throat and a cough. The whole snotty works.

A few weeks later she thought she had recovered. Then her husband Derek got sick, and bam. 'Suddenly I started getting all the symptoms [again] and it was worse,' said Ms. Gilbert, a 61-year-old writer in Charleston, Ill.

In the winter that seems to have no end in many parts of the country, people like Ms. Gilbert have been plagued with the seemingly everlasting cold.

That's partly because the common cold can last longer than many people think -- up to two weeks for the principal symptoms and perhaps weeks more for a cough that lingers even after the virus has been cleared away. There's also the possibility of secondary infections such as bacterial sinusitis.

And some patients might get back-to-back colds, doctors say. It isn't likely people will be reinfected with the same virus because the body builds some immunity to it. But people can pick up another of the more than 200 known viruses that can cause the common cold, some of which are worse than others.

'When you hear people who have the cold that 'won't go away,' those are typically back-to-back infections of which we see a lot of in the cold weather when people are cohorting together,' said Darilyn Moyer, a physician at Temple University Hospital and chairwoman-elect of the American College of Physicians Board of Governors.

Influenza may get all the attention, but the common cold is the leading cause of doctor visits, according to the National Institutes of Health. Each year, people in the U.S. get about one billion colds, and 22 million school days are lost to the stubborn viruses.

Experts say adults on average get two to five colds a year; school children can get as many as seven to 10. The elderly tend to get infected less because they've built up immunity to many viruses. And adults who live or work with young children come down with more colds.

Don't I know it. For more than a month now my family seems to be playing a game of pass-the-nasty-cold. My husband had a cold and lingering cough for weeks, which we suspect he gave to our infant. Finally I succumbed.

We blamed the purveyor of all germs, our kindergartner. Just as we were all recovering, the infant started day care and brought home a virus and we're all on round two of apparently a different cold.

Experts say it's possible that the carrier of germs -- in this case our kindergartner -- can infect others without having symptoms himself.

'At any given moment if we were to swab you. . .we'd probably come up with five different rhinoviruses sitting in your nose but you're not sick,' said Ann Palmenberg, a researcher at the Institute of Molecular Virology at the University of Wisconsin-Madison. Rhinovirus is the most common viral cause of the common cold, accounting for 30% to 50% of adult colds, and there are more than 150 strains of it.

To get infected, the so-called ICAM receptors, which the rhinovirus attaches to in order to enter the nasal cells, need to be open, Dr. Palmenberg said.

'Rhinos are out there all the time, it's just a question of when you are susceptible,' she said. Factors such as stress, lack of sleep and people's overall health can make them more likely to get infected. More than 150 strains or genotypes of the rhinovirus have been identified and researchers believe there are probably many more.

Rhinovirus replicates best in the relatively lower body temperatures of the upper respiratory area, such as the nasal passages, sinuses and throat.

Other viruses, such as the less-common adenovirus, can replicate and attach to receptors in the upper and lower respiratory tracts, causing a more serious illness.

Other viruses -- including the coronavirus, respiratory syncytial virus and enterovirus -- have also been identified as causing cold symptoms. 'The most confounding thing of all is that we still haven't identified the cause of 20% to 30% of adult common colds,' said Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health.

Sometimes a cold that never seems to end could be a sign of something more serious. A cold may result in a sinus infection, bronchitis or pneumonia. And cold symptoms are at times confused with seasonal allergies.

A usually dry cough that lingers after a cold is typically due to bronchial hyperreactivity or tracheal inflammation, doctors say. 'After you go through an infection in your respiratory system, you can almost have a transient form of asthma where your bronchial tubes are very highly reactive and very irritated and inflamed,' said Dr. Moyer, of Temple University Hospital.

A review of various studies, published last year in the journal Annals of Family Medicine, found that coughs on average last about 18 days. The report also said a survey of nearly 500 people found that most participants expected a cough should disappear in about a week and believed antibiotics from their doctor would help them. (A big no-no!)

Some experts believe having one cold virus and a weakened immune system could make catching another virus easier. Because the epithelial linings in the nose are weakened when you have a cold, the broken down mucus-membrane barrier may be more prone to picking up another virus.

But others suggest that proteins such as interferons, which are secreted during a cold to help fight the virus, may also boost resistance to getting infected by a second virus, according to Dr. Fauci, of the NIH.

What can a person do to prevent or shorten a cold? Nearly everyone knows someone who swears by taking echinacea or zinc or downing packs of vitamin C.

But doctors say the evidence isn't conclusive that any of these remedies helps. Some research indicates that exercise and meditation could help prevent colds.

The good news is spring is here, at least officially, so the worst of the winter cold season should be over. Come summer, however, a new batch of viruses emerge and you might find yourself saying hello to the pesky summer cold.

《华尔街日报》—大约在一个月前,莎伦·吉尔伯特(Sharon Gilbert)出现了流涕、咽喉疼痛、咳嗽等一系列令人烦恼的症状。

几个星期后,她觉得自己已经康复了。可是,接下来她的丈夫德里克(Derek)又病了,而且猛地一下,“突然间我开始(再次)出现所有的症状,而且这次更严重了,”吉尔伯特说道。今年61岁的她是伊利诺伊州查尔斯顿(Charleston)的一名作家。

在美国众多冬季似乎没有尽头的地区,像吉尔伯特这样的人一直受到似乎永不休止的感冒的折磨。

一部分原因是,普通感冒的持续时间要比许多人所认为的更长——主要症状会持续长达两周时间,至于在感冒病毒已被清除后仍久不见愈的咳嗽,它可能要再持续几周时间。此外,患上细菌性鼻窦炎之类的继发性感染的可能性也存在。

医生说,有些患者或许会连续患感冒。人们不大可能会重新感染同一种病毒,因为人体已对它形成了一定的免疫力。然而,能引发普通感冒的已知病毒有200多种(有些病毒比其他更厉害),人们还是会感染上其中一种。

天普大学医院(Temple University Hospital)医生、美国医师协会(American College of Physicians)理事会候任主席达尔琳·莫耶(Darilyn Moyer)说:“如果你听到别人得了‘永不见好’的感冒,那通常就是连续性感染,这种情况在人们常窝在一起的寒冷季节较多见。”

美国国家卫生研究院(National Institutes of Health,简称“NIH”)称,流感吸引了人们所有的注意力,但普通感冒才是人们就医的首要原因。美国每年约有10亿人次得感冒,学生们因顽固的感冒病毒共停课2,200万天。
专家们说,成年人每年平均患两到五次感冒,学龄儿童的感冒次数则多达七到10次。老年人感染病毒的次数往往较少,因为他们已经形成了对多种病毒的免疫力。与儿童生活在一起或者工作中与儿童接触的成年人感冒较多。

对此我是深有体会。最近一个多月来,我们家似乎就在玩讨厌的感冒传递游戏。我的丈夫得了感冒,又持续咳嗽了几周时间,我们怀疑他又传染给了我们幼小的孩子。最后我也倒下了。

我们认为我们上幼儿园的孩子是各种病菌的传播者。就在我们大家逐渐康复时,孩子开始上日托了,把某种病毒带回了家,于是我们全都开始了新一轮明显与第一次不同的感冒。

专家指出,病菌携带者——在我们家则是我们上幼儿园的孩子——有可能会将病菌传染给别人,而自己不会出现症状。

威斯康星大学麦迪逊分校(University of Wisconsin-Madison)分子病毒学研究所(Institute of Molecular Virology)的研究员安·帕尔门伯格(Ann Palmenberg)说:“在任何时候,要是我们用棉签擦拭你的鼻子,大概都能发现它里面存在着五种不同的鼻病毒,但是你也并没有生病。”鼻病毒是引发普通感冒最常见的病毒,占成年人感冒诱因的30%至50%,而且它的种类超过了150种。

帕尔门伯格博士指出,鼻病毒附着在细胞间黏附分子(ICAM)受体上以便进入壁细胞,在该受体张开时,人们才会感染病毒。

她说:“鼻病毒一直都存在,问题在于你什么时候会变得易受感染。”压力、缺乏睡眠和总体的健康状况等因素会使人们更容易感染。研究人员已发现了鼻病毒的150多种菌株或基因类型,他们相信可能还存在更多。
病毒在上呼吸道区体温相对较低的环境(如鼻通道、鼻窦和咽喉)中复制最快。

其他病毒(如较少见的腺病毒)能在上呼吸道与下呼吸道自我复制并附着在受体上,引发更严重的疾病。

包括冠状病毒、呼吸道合胞病毒和肠道病毒在内的其他病毒也被确认会引发感冒症状。NIH的分支、美国国家过敏症与传染病研究所(National Institute of Allergy and Infectious Diseases)主任安东尼·福西(Anthony Fauci)说:“最令人困惑的事情是,还有20%至30%成年人普通感冒病症的原因未查明。”

有些情况下,似乎永不休止的感冒可能是更严重病症的信号。感冒有可能引发鼻窦感染、支气管炎或肺炎,而有时候感冒症状又会被误认为是季节性过敏。

医生指出,感冒之后持续的干咳通常是由支气管高反应性或气管感染造成的。天普大学医院的莫耶医生说:“你的呼吸系统经历了感染后,基本上你会出现暂时性的哮喘,你的支气管反应会非常剧烈,感染和炎症也会很严重。”

去年发表于《家庭医学年鉴》(Annals of Family Medicine)的一篇论文对多项不同研究进行了综述,它发现咳嗽平均持续18天左右。该研究还指出,针对近500人的调研发现,大多数调研参与者认为咳嗽症状应该会在一周左右后消失,并相信医生开给他们的抗生素对他们有帮助。(实际上是大大的不可能!)

有些专家认为,在感染了一种感冒病毒、免疫系统减弱后,你会更容易感染另一种病毒。这是因为当你感冒时你鼻内的上皮衬里会变弱,充当保护屏障的黏膜受损后可能更易于感染另一种病毒。

但是,另一些专家则持有不同看法。NIH的福西医生说,干扰素之类的蛋白质(在感冒期间分泌以帮助抵抗病毒)可能会提高对感染第二种病毒的抵抗力。

那么,我们能做些什么来防止感冒或缩短感冒时间?几乎每个人都认识一些深信服用紫锥菊、锌或吞下大量维生素C有效的人。

然而,医生指出,没有确凿的证据能证明这些疗法有效。有些研究指出,运动和冥想可能有助于防止感冒。

好消息是,春天来临了(至少名义上如此),冬季最糟糕的寒冷时节就要结束了。不过,到了夏天,又会有新一批的病毒出现,你也许会发现自己又和讨厌的夏季感冒碰面了。

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