Common cold - kanbou (kaze) (English spelling)

Japanese: 感冒（かぜ） - かんぼう（かぜ）（英語表記）Common cold

What is the disease?

The airway that passes through the lungs is called the respiratory tract. The area from the nose and mouth to the vocal cords is called the upper respiratory tract, and the area behind that, the bronchi, is called the lower respiratory tract. A cold is an inflammatory disease of the upper respiratory tract. Upper respiratory tract infection ( Public transport ) Inflammation of the lower respiratory tract is bronchitis ( Kidney exam ) And further in, the inflammation in the lungs pneumonia ( Haien ) However, it seems that even simple bronchitis is often referred to as a cold.

When the cold virus shown in "What is the cause?" enters the body through the nose or mouth and adheres to and invades the mucous membrane cells of the upper respiratory tract (this is called infection), Exudative ( Newcomer ) Inflammation of the phlegm, that is, mucus secretions appear and the symptoms shown in "How symptoms appear" occur. If the mucus is mainly white or transparent, it is a viral inflammation, but if the phlegm is colored, it has progressed to a secondary bacterial infection, and antibiotic treatment is required.

What is the cause?

More than 90% of colds are caused by viral infections, but Streptococcus ( Yorenkin ) Bacteria such as mycoplasma and chlamydia are involved. Cold and dry weather can trigger colds, but it is also well known that colds are more common in periods with large daily temperature differences, such as late autumn and early spring, than in the harsh winter.

There are more than 100 types of viruses that cause colds (cold viruses), but there are about 10 major types.

- Rhinoviruses and coronaviruses that mainly cause colds regardless of the season

- Enteroviruses, echoviruses, and coxsackieviruses, which are likely to cause stomach symptoms such as stomach pain and diarrhea, especially in the summer

Adenoviruses and parainfluenza viruses, which are common in spring and autumn colds

- RS virus, which is common in winter and can cause severe pneumonia in children

・Influenza virus (influenza virus pneumonia)

Examples include:

Most colds are strongly related to the season (Figure 1), and cold triggers include dryness, cold, temperature changes, fatigue, lack of sleep, etc. Of course, most colds are infectious, so the biggest trigger and cause is the prevalence of colds in the surrounding area.

How symptoms manifest

Symptoms vary slightly depending on the type of virus (Figure 2). Usually, after 1-2 days of fatigue, chills, and dry throat and nose, symptoms such as sore throat, runny nose, stuffy nose, headache, and fever appear. In many cases, symptoms will improve immediately, but cough ( cough ) Coughing and expectoration of phlegm means that the inflammation has begun to spread to the lower respiratory tract, and symptoms, including fever, become more severe.

However, these symptoms are normal defense reactions that kill the invading virus by applying heat or dissolve it in mucus to weaken it and expel it from the body as phlegm. Therefore, unless the symptoms are causing a loss of strength, it is best to not try to reduce fever or cough unnecessarily. Town ( Shizu ) It's not a good idea to do it too much.

However, the substances produced in the body to fight off the virus (known as inflammatory cytokines, etc.) can cause side effects such as headaches, fatigue, runny nose, sore throat, high fever, and loss of appetite. Small children may experience systemic symptoms such as abdominal pain, diarrhea, and vomiting. These weakening symptoms need to be suppressed, and treatment for this (antipyretics, analgesics, intestinal regulators, intravenous drip, etc.) is called symptomatic treatment, and is an important treatment for colds.

By the way, how many times a year do humans catch a cold? Some statistics suggest that children catch colds on average more than four times a year, adults more than two times, and people under the age of five more than eight times a year, their mothers more than five times, and their fathers more than four times. However, since it is easy to forget about mild colds, the actual number may be even more than that.

Testing and diagnosis

Anyone can recognize the symptoms of a cold, but it is difficult for doctors to distinguish between a virus and a bacterial cold, so even if you have a simple cold, you will be examined thoroughly. First, you will be asked about your medical history, when your symptoms started and how they have changed, if you have taken any over-the-counter medicines, how they have changed, and whether there is anyone around you with similar symptoms.

During the examination, Tonsils ( Tonsil ) There are no red spots or spots, or the area has turned white ( White moss ( Pact ) ) and yellow suppuration. Examination ( fruit ) We will also check for swelling of lymph nodes in the neck, and abnormalities in the eyes, nose, and skin. We will listen to the sounds of the lungs with a stethoscope to check for the spread of pneumonia or bronchitis.

The symptoms and changes (observations) that appear in the body vary depending on the type of virus or bacteria, so this is how we examine you. To be precise, we swab the back of your nose and throat and examine what kind of virus is in there, or what parts of each virus are unique ( Specific antigen ( Special promotion ) ) is included.

In some cases, blood samples are taken to check the white blood cell count (usually decreased if the infection is caused by a virus, and increased if the infection is caused by bacteria) and to check the inflammatory response (CRP, etc.). We may also check to see which viruses have increased immunity (antibodies), but since antibodies only increase once the patient has recovered, blood tests are often performed after the patient has recovered. A chest X-ray is also taken to check for pneumonia.

There may be other diseases that resemble a cold, and checking for their presence or absence is called a differential diagnosis. The most important disease to distinguish is Hay Fever ( Coffee ) Allergies such as bronchitis and pneumonia in the lower respiratory tract, pulmonary tuberculosis ( Haikekaku ) , lung cancer, etc. Many of these have symptoms that are slightly different from a cold and tend to be stronger or last longer, so if you experience any of these symptoms, consult a doctor immediately.

Treatment methods

Treatment for colds can be broadly divided into two categories (Figure 3). One is symptomatic treatment, which suppresses symptoms that weaken the body, as mentioned in the "Symptoms" section.

These include antipyretics, analgesics, anti-inflammatories, gargles, intestinal regulators, and infusions, but the most well-known example is a general cold medicine that combines antipyretics, analgesics, and anti-inflammatory ingredients in one tablet or powder. There are many types of general cold medicines, and they are slightly different, especially those that suppress runny nose or headaches, so please consult a pharmacist at the pharmacy.

The other is causal therapy. This is a fundamental treatment that directly eradicates the viruses and bacteria that cause colds (which often develop following a viral infection). There are many antibiotics that are effective against bacteria, but there are no drugs that are effective against cold viruses other than influenza viruses. There is a particular need for treatments for respiratory syncytial virus, which can lead to severe illness, and coxsackie virus, which can cause cardiac complications.

What about herbal medicines? Some over-the-counter cold medicines contain herbal ingredients. In fact, in recent years, it has been discovered that the ingredients in herbal medicines regulate the inflammatory cytokines (of which there are many types) mentioned in "How symptoms appear" in various ways, thereby calming the various symptoms of colds and influenza. It is beginning to be scientifically elucidated that the mechanism by which herbal medicines, which have been created empirically, work is actually rational. If this elucidation progresses further, it is likely that herbal medicines will become more widely used.

What to do if you notice an illness

Usually, there is no need to see a doctor right away if you have a cold. This is because colds can often be cured with rest and over-the-counter cold medicine. If you stay at home and keep warm and moisturized, and get enough nutrition and sleep, you will recover within a few days.

However, in some people, the disease can progress to bronchitis, pneumonia, or even heart failure. Who are the people most likely to develop such complications? In fact, the people listed in the next section on influenza as those who should get vaccinated are those who are most likely to develop such complications.

That is, people generally aged 65 or older, people living in groups in facilities such as nursing homes, people with chronic lung or heart disease, people receiving treatment for diabetes or kidney disease, children receiving aspirin treatment, and pregnant women in the 14th week or later of pregnancy, during which influenza is prevalent. These people are more likely than others to develop severe colds and influenza and progress to pneumonia, so they should see a doctor early.

Akira Watanabe

Figure 1 Seasons and winds
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Figure 1 Seasons and winds

Figure 2. Virus types and cold disease types
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Figure 2. Virus types and cold disease types

Figure 3. Treatment policy for colds (acute upper respiratory tract infections)
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Figure 3. Treatment policy for colds (acute upper respiratory tract infections)

Source: Houken “Sixth Edition Family Medicine Encyclopedia” Information about the Sixth Edition Family Medicine Encyclopedia

Japanese:

どんな病気か

　肺に出入りする空気の通り道を気道といいますが、鼻や口から声帯までを上気道、その奥の気管支を下気道といいます。かぜは上気道の炎症性の病気なので上気道炎(じょうきどうえん)ともいいます。下気道の炎症は気管支炎(きかんしえん)であり、さらに奥にある肺の炎症は肺炎(はいえん)ですが、単純な気管支炎までをかぜという場合が多いようです。

「原因は何か」に示すかぜウイルスが鼻や口から侵入して上気道の粘膜の細胞に吸着・侵入（これを感染という）すると、滲出性(しんしゅつせい)の炎症、すなわち粘液性の分泌物が出て「症状の現れ方」に示す症状が起こります。白色や透明感のある粘液が主であればウイルス性の炎症ですが、痰に色がついている場合は細菌の2次感染に進行しているので、抗菌薬治療が必要になります。

原因は何か

　かぜの原因の9割以上はウイルス感染ですが、一部に溶連菌(ようれんきん)などの細菌やマイコプラズマ、クラミジアが関係します。寒冷や乾燥などはかぜの誘因ですが、厳寒期よりも晩秋や春先など1日の気温差が激しい時期にかぜが多いこともよく知られています。

　かぜを起こすウイルス（かぜウイルス）を詳しく数えれば100種類以上もありますが、代表的なものは約10種類です。すなわち、

・季節にあまり関係なく主に鼻かぜを起こすライノウイルスやコロナウイルス

・夏を中心に腹痛、下痢などおなかの症状を伴いやすいエンテロウイルスやエコーウイルス、コクサッキーウイルス

・春や秋のかぜに多いアデノウイルスとパラインフルエンザウイルス

・冬に多くて子どもに重症の肺炎を起こすことのあるRSウイルス

・インフルエンザウイルス（インフルエンザウイルス肺炎）

などが代表です。

　かぜの多くは季節との関連が強い（図1）のですが、かぜの誘因には乾燥や寒冷、温度変化などのほかに、疲労や睡眠不足などもあります。もちろん、かぜのほとんどは感染症ですから、周囲にかぜが流行していることが最大の誘因であり、原因であるといえるでしょう。

症状の現れ方

　ウイルスの種類によって症状は少しずつ異なります（図2）。通常、体のだるい感じや寒気、のどや鼻の乾燥感などが1～2日続いたあと、のどの痛みや鼻水、鼻づまり、頭痛、発熱などが現れます。そのまま治ることも多いのですが、引き続いて咳(せき)や白っぽい粘液のような痰が出たりします。咳や痰が出ることは、炎症が下気道へも広がり始めたことを意味しており、発熱も含めて症状はさらに強くなります。

　しかし、これらの症状は侵入したウイルスに熱を加えて退治したり、粘液に溶かし込んで弱らせながら痰として体外に排出したりする正常な防御反応ですから、体力を損うような症状でなければむやみに解熱したり咳を鎮(しず)めすぎたりするのは考えものです。

　ただ、ウイルスを退治するために体内で生産される物質（炎症性サイトカインなどという）は頭痛やだるさ、鼻水、のどの痛み、高熱、食欲不振などの副反応を引き起こします。小さな子どもでは、腹痛や下痢、嘔吐などの全身症状が出ます。こうした体力を弱らせる症状は抑える必要があり、その治療（解熱薬、鎮痛薬、整腸薬、点滴など）を対症療法といって、かぜの大切な治療法のひとつです。

　ところで、ヒトは年に何回くらいかぜをひくのでしょうか。子どもは年に平均4回以上、大人は2回以上とか、5歳以下は年8回以上、その母親は5回以上、父親も4回以上とする統計などがありますが、軽いかぜのことは忘れやすいので、それ以上かもしれません。

検査と診断

　かぜの症状は誰でもわかりますが、どのウイルスが原因なのか、細菌によるかぜなのかの判別は医師にも難しいので、単なるかぜでも診察は綿密に行われます。最初に病歴や、どんな症状がいつから起こり、どのように変化したか、市販薬をのんだ場合はどのように変化したか、まわりに似た症状の人はいないか、などが聞かれます。

　診察では、のどや扁桃(へんとう)に赤みや斑点がないか、白くなって（白苔(はくたい)）いないか、黄色い化膿がないかなどを診(み)ます。また、首のリンパ節のはれ、眼や鼻、皮膚の異常なども調べます。肺炎や気管支炎などへの広がりを確かめるためには、聴診器で肺の音を聞きます。

　ウイルスや細菌の種類によって症状や体に現れている変化（所見）が違うのでこのように診察するのですが、正確には鼻の奥やのどを綿棒でこすり、そのなかにどのようなウイルスがいるのか、あるいはそれぞれのウイルスに特有な部品（特異抗原(とくいこうげん)）が含まれているかどうかを調べます。

　場合によっては血液をとって白血球の数を調べたり（ウイルスによる場合は通常減り、細菌による場合は増える）、炎症反応（CRPなど）を調べたりします。どのウイルスに対する免疫（抗体）が増えているのかを調べることもありますが、抗体は治るころになってようやく増えるので、具合がよくなってから血液検査をすることが多いのです。また、肺炎になっていないかどうかを確認するために胸部X線検査を行います。

　かぜと似た他の病気が隠れていることがあり、それらの有無について調べることを鑑別診断といいます。区別すべき最大の病気は、上気道では花粉症(かふんしょう)などのアレルギー、下気道では気管支炎や肺炎、肺結核(はいけっかく)、肺がんなどです。これらの多くは、かぜとは症状がやや違って強かったり長く続いたりするので、その場合はすぐ医師に相談してください。

治療の方法

　かぜの治療は大きく2つに分けられます（図3）。「症状の現れ方」で述べた、体力を弱らせてしまうような症状を抑える対症療法がそのひとつです。

　解熱薬、鎮痛薬、抗炎症薬、うがい薬、整腸薬、点滴などですが、解熱成分、鎮痛成分、抗炎症成分などをひとつの錠剤や散剤にまとめた総合感冒薬がその代表です。総合感冒薬には多くの種類があり、とくに鼻みずを抑えるもの、頭痛を抑えるものなど、少しずつ違うので、薬局の薬剤師に相談してください。

　もうひとつは原因療法です。かぜの原因であるウイルスや細菌（ウイルス感染に続いて発症することが多い）を直接退治する根本的な治療です。細菌に効く抗菌薬はたくさんありますが、インフルエンザウイルス以外のかぜウイルスに効く薬はまだありません。重症になりやすいRSウイルスや心臓の合併症が出やすいコクサッキーウイルスなどは、とくに治療薬がほしいものです。

　漢方薬はどうでしょうか？　市販の感冒薬にも漢方成分を配合した薬があります。実は近年、漢方薬の成分が、「症状の現れ方」で述べた炎症性サイトカイン（たくさんの種類がある）をさまざまに調節して、かぜやインフルエンザの諸症状を鎮めることがわかってきました。経験的につくられてきた漢方薬のはたらく仕組みが、実は合理的であることが科学的に解明され始めたのです。解明がさらに進めば、漢方薬がもっと使われるようになると思われます。

病気に気づいたらどうする

　かぜは通常、すぐに受診する必要はありません。安静や市販の感冒薬で治ることが多いからです。自宅で保温と保湿を十分にし、栄養と睡眠をしっかりとれば、数日で治ります。

　しかし、一部の人では気管支炎や肺炎に進んだり、心不全にまで進んだりします。どのような人がそうした合併症を起こしやすいのでしょうか？　実は、次のインフルエンザの項でワクチンを打つべき人としてあげられている人たちがそうなのです。

　すなわち、おおむね65歳以上の高齢者、老人ホームなどの施設で集団生活をしている人、慢性の肺の病気や心臓病の人、糖尿病や腎臓病などで治療を受けている人、アスピリンによる治療を受けている小児、妊娠14週め以降がインフルエンザの流行期に該当する妊婦などです。こうした人々はそれ以外の人に比べてかぜやインフルエンザが重症化しやすく、肺炎などに進みやすいので、早めに医師の診察を受けてください。

渡辺　彰

図1　季節とかぜ
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図1　季節とかぜ

図2　ウイルスの種類とかぜの病型
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図2　ウイルスの種類とかぜの病型

図3　かぜ（急性上気道炎）の治療方針
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図3　かぜ（急性上気道炎）の治療方針

出典　法研「六訂版家庭医学大全科」六訂版家庭医学大全科について　情報

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