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What is a cold?(1)


Illustration of a boy wearing a mask after catching a cold


What is a cold?

Cold is one of the most common illnesses throughout the year and is also called "cold syndrome" or "cold".


Cold symptoms usually recover in about a week, but prolonged symptoms can cause serious complications such as pneumonia.

Therefore, it is important to take the cold medicine that suits your symptoms as soon as possible.


Cold is a familiar illness in daily life, but what kind of illness is it?

A cold is an acute inflammatory disease in the upper respiratory tract, such as the nasal cavity and pharynx, caused primarily by a viral infection.

Inflammation often extends beyond the local area to the entire airways.

When you catch a cold, you may experience symptoms such as sneezing, runny nose, stuffy nose, coughing, sputum, sore throat, and fever.


Influenza is also included in colds in a broad sense, but colds are caused by severe systemic symptoms such as high fever, headache, arthralgia, and malaise, which are easily aggravated, and are extremely infectious and cause a large-scale epidemic. It is taken as a distinction from.


80-90% of colds are caused by viruses.

In addition, there are non-infectious ones such as infection by bacteria including mycoplasma, allergies and cold.

The main viruses that cause colds include rhinovirus, coronavirus, influenza virus, parainfluenza virus, and adenovirus, and it is said that there are more than 200 types.

Rhinovirus infections are especially common, and most adult colds are due to this.


In addition, the symptoms of colds vary depending on the type of virus that infects.

"Nasal cold" with runny nose and stuffy nose is mainly caused by leprosy virus and coronavirus, and "throat cold" which is common in summer and causes pain and swelling in the throat is mainly caused by adenovirus. Will be.


However, with some exceptions such as influenza, it is difficult to identify the causative virus from the symptoms.

In addition, even if you can immunize against the infected virus, you will repeatedly catch colds because the immune effect does not continue and there are many variants of the virus.


Transmission route and symptoms

There are three virus infection routes: contact infection, droplet infection, and air (droplet nucleus) infection.

Contact infections are transmitted through the mucous membranes of the mouth and nose through the hands.

Droplet infection is transmitted when another person inhales the virus contained in the droplets scattered by coughing or sneezing through the mouth or nose.

Airborne infections are transmitted by inhaling viruses in particles that are scattered over a wide area and are floating in the air.

In the case of colds, contact infections and droplet infections are the most common, with hand-borne contact infections being the most common.


Factors Affecting Cold Susceptibility

If you are stressed or tired and weak, your resistance to the virus will decrease and you will be more likely to catch a cold.

Especially at the turn of the season, the temperature changes, which makes it even easier to pull.

Elderly people have weakened reflexes such as coughing and sputum excretion as well as resistance.

Be especially careful if you are bedridden or have a chronic chronic illness.

Children are more likely to come into contact with the virus through group life such as school, so be careful during the epidemic.


Course of Cold Symptoms

Cold symptoms generally have the following course:

When infected with the virus, after an incubation period of 1 to 3 days, the initial symptoms are discomfort in the nose and throat, and sneezing, runny nose, and sore throat appear.

Symptoms such as cough, sputum, fever and headache appear in the middle stage (3-4 days later), and systemic symptoms such as coughing and joint pain appear in the latter stage.


Understanding the Respiratory System

Before we take a closer look at the symptoms of the common cold, let's take a look at how and how the respiratory system works.


Respiratory System Overview

Respiratory refers to the nasal cavity, throat (pharynx, larynx), trachea, bronchi, lungs, etc. that are involved in breathing.

The main function of the respiratory tract is to inhale, take in the oxygen that the body needs, and exhale carbon dioxide into the atmosphere.

The airway from the nasal cavity to the lungs is called the "airway" and plays a role in delivering clean air to the lungs.


The airways are divided into the upper respiratory tract from the nasal cavity to the pharynx and larynx and the lower respiratory tract of the trachea and bronchi.

Since the respiratory system takes in oxygen from the outside air, it is constantly exposed to the outside world.


Therefore, it can be said that the respiratory tract is an organ that is easily infected by foreign substances such as viruses that exist in the outside air.

Therefore, the respiratory system has a protective reaction that protects the lungs and trachea from foreign substances such as dust and viruses that come in from the outside.

Sneezing, runny nose, and coughing are one of the protective reactions.


The Role of Histamine in Cold Symptoms

Histamine, a chemical mediator, plays a major role in the mechanism by which cold symptoms occur.

Here, we will look at how histamine causes cold symptoms.


Symptoms of a Common Cold


A pet dog watches over a woman who can't stop sneezing and a runny nose


Most colds cause early sneezing, runny nose, and stuffy nose because the virus often infects the mucous membranes of the nose and throat first.

When the virus infects the mucous membrane of the nose and causes inflammation, histamine is secreted at the site of inflammation.


When this histamine stimulates the sensory nerves, the stimulation is transmitted to the sneezing center, causing sneezing and trying to eliminate the virus from the body.

The stimulus is also transmitted to the secretory center, which works to drain the runny nose and wash away the virus.


In addition, histamine directly stimulates blood vessels in the nasal mucosa, causing nasal congestion due to vasodilation, congestion, and edema.


Throat pain is manifested by a virus infecting the mucous membranes of the throat and causing inflammation.

When the inflammation becomes severe and the tonsils and lymph nodes become red, the pain becomes even stronger and even swallowing saliva becomes painful.

Cough and sputum are reactions that try to eliminate secretions in the trachea and foreign bodies from the outside.


The airway mucosa includes fine hairs (pilus) and the airway mucosa that covers the surface, and moisturizes and protects the surface of the mucosa.

The invading virus becomes entangled in the airway mucosa and becomes sputum as it travels through the airways.


Sputum is excreted by pili movement and coughing commanded by the coughing center of the brain.

Cough includes dry cough without sputum and wet cough with sputum.

Wet cough, which is common during the convalescent period, works as sputum to eliminate the virus, and in order not to exacerbate the infection, try to get it out as much as possible without forcibly suppressing it.


Fever is also one of the defense reactions that protects you from viruses.

Body temperature is usually kept constant by the thermoregulatory center in the hypothalamus.

When a virus invades the body, white blood cells and other biological defense substances attack the virus and secrete cytokines.

Cytokines stimulate the production of prostaglandins, which instruct the thermoregulatory center to raise body temperature.

The blood vessels in the skin then contract, the sweat glands close, and heat dissipation is suppressed.


At the same time, it causes the muscles to shake and raises the body temperature by producing heat.

Prostaglandins are also associated with headaches and muscle soreness because they enhance the action of pain-causing substances.

So why raises body temperature?

When the body temperature rises, the growth of viruses that prefer low temperatures can be suppressed, and the function of white blood cells becomes active, so the immune function increases.


For this reason, the body that has been invaded by the virus tries to protect itself by fever and raising the body temperature.

However, fever due to a cold usually does not exceed 38 degrees Celsius and will heal in about 3 days.



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