Causes of the Common Cold

It was not until the 1950s that it was discovered that the cause of the common cold is a virus, and about two-thirds to three-quarters of colds are caused by viruses. About 5-10% are caused by a bacterium called Group A streptococcus, and in some cases the cause cannot be identified.

1. Virus Among the viruses that cause colds, the most common is rhinovirus, followed by coronavirus, respiratory syncytial virus, influenza virus, parainfluenza virus, and others. In addition, adenovirus, enterovirus, rubella virus, and measles virus can also be causes, though rarely.

More than 100 different types of rhinoviruses are known. For this reason, people catch colds often, and even after a cold has completely healed, they can catch another one again. In the case of a cold caused by rhinovirus, unlike hepatitis vaccines or flu vaccines, there is still no vaccine that can prevent it.

1. Virus A virus is an independent life form that can cause disease in humans. Unlike bacteria, it cannot live on its own and can multiply only by parasitizing living cells. It is smaller than bacteria and varies in size and shape, but it is composed of a genetic material area called nucleic acid and a protein shell.

2. Avian influenza Among type A influenza viruses, avian influenza refers to the type that causes influenza not in humans but in chickens, ducks, wild poultry, and pigs. Currently, avian influenza has been widespread in eight countries: Korea, Japan, Vietnam, Thailand, China, Indonesia, Laos, and Cambodia. Among them, in 1997, there was a case in Hong Kong where it first occurred in humans rather than birds and the patient died, and there were similar cases in Vietnam and Thailand. Fortunately, there have been no reports of cases occurring in humans in Korea.

3. SARS At the early stage of infection, symptoms vary and include fever, muscle pain, fatigue, chills, dry cough, and in severe cases even shortness of breath. The first patient appeared in China in 2002, and infection was later confirmed in Taiwan and Singapore, with suspected cases reported in Korea. The cause is a new variant of coronavirus, which causes viral pneumonia and has a high mortality rate. There is still no treatment with proven effectiveness.

2. Bacteria Some cases of the common cold are caused by bacteria, and Group A streptococcus is the most common cause, with pyogenic streptococcus being the most common.

3. Frequency of Colds and Other Causes

1. Season and climate In temperate climates with distinct four seasons, like Korea, colds mainly occur more often in winter. In the past, elders said that if the body felt chilled, you would catch a cold. In traditional Korean medicine, the term "sanghan" is also used for this reason.

In cases caused by rhinovirus, the number of patients rises sharply in spring and fall. Contrary to common sense, exposure to cold temperatures does not seem to make people catch colds more often. Rather, because people spend more time indoors in winter, they have more opportunities to come into contact with people who already have colds, and it is assumed that the cause may be the different humidity levels in each season. In the case of influenza, it mainly occurs in winter from October to April of the following year, and because it spreads easily between people, it is highly contagious and highly infectious, causing sudden outbreaks. In tropical regions, it is said that colds are more common during the rainy season.

2. Age When are colds caught most often? During early childhood under the age of 5, the frequency is highest over the course of a person's life. After growing up through many illnesses and accidents and becoming an adult, fortunately the chances of catching a cold decrease.

3. Environment Because infections spread easily to the household by children infected at daycare centers or schools, colds occur more often when there are children in the home. It is hard to say who caught it first, but you have probably experienced many cases where mothers, fathers, and babies caught colds one after another. Now you know why parents tell children to wash their hands and feet first when they come back from school.

4. Other causes Smoking is said to make people more likely to catch colds, and stress, which everyone in modern society has to some degree, can also be a cause. Quitting smoking helps not only prevent cancer and cardiovascular disease, but also helps prevent colds.

So far, I have explained the causes of colds. In the next part, we will take a closer look at the symptoms of colds.

Source: Korea Centers for Disease Control and Prevention, National Health Information Portal