Common colds: Symptoms, causes, complications, and treatment

The common cold is a viral infectious disease that infects the upper respiratory system. It is also known as acute viral rhinopharyngitis and acute coryza.

It is the most common infectious disease in humans and is mainly caused by coronaviruses or rhinoviruses.

Because there are more than 200 viruses that cause the common cold, the human body can never build up resistance to all of them. This is why colds are so common and often return. According to the CDC (Centers for Disease Control and Prevention), adults get 2–3 colds per year, and children may have up to 12 per year.

The common cold is contagious; it can be spread by air droplets from coughs and sneezes and by touching infected surfaces. It is contagious from 1–2 days before symptoms begin until the symptoms have stopped.

Fast facts on colds

Here are some key points about colds. More detail and supporting information is in the main article.

Common cold symptoms include dry or sore throat, blocked or runny nose, and sneezing.

Around a quarter of people do not experience symptoms when infected with a cold.

Up to half of common colds are caused by a group of viruses referred to as rhinoviruses.

Complications of the common cold include acute bronchitis and pneumonia.

People with lung conditions such as asthma and chronic obstructive pulmonary disease are more vulnerable to colds than other people.


Man and woman with common cold
The symptoms of common cold are well known to most people.

The symptoms of the common cold are the body’s reaction to the cold virus. It triggers the release of chemicals, making the blood vessels leak, causing the mucous glands to work harder.

The most common symptoms of a cold are:

dry throat

sore throat


mild fever


hoarse voice

blocked nose

mild headache

Rarer symptoms of a cold include:

muscle aches


pink eye


reduction in appetite

extreme exhaustion

Some people do not suffer any symptoms when infected with the cold virus, perhaps because their immune system reacts differently to the virus. Sometimes, bacteria can infect the ears or sinuses during this viral infection — this is known as a secondary bacterial infection — and can be treated with antibiotics.


The common cold can be caused by more than 200 different viruses. Around 50 percent of colds are caused by rhinoviruses, other cold-causing viruses include:

human parainfluenza virus

Human metapneumovirus

coronaviruses adenovirus

human respiratory syncytial virus


When a virus manages to overpower the body’s immune system, infection occurs. The first line of defense is mucus, which is produced in the nose and throat by the mucus glands. This mucus traps anything inhaled, such as dust, viruses, and bacteria. Mucus is a slippery fluid that the membranes of the nose, mouth, throat, and vagina produce.

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When the mucus is penetrated by the virus, the virus then enters a cell, the virus takes control and uses the cell’s machinery to manufacture more viruses, and these viruses then attack surrounding cells.

Older adult
Older adults are more at risk of catching a cold.

Some people are more susceptible to the common cold than others, including:

children under 6

older adults

individuals with weak immune systems


Anyone who has been around infected individuals is also at risk; for instance on an airplane or at school. Also, people are more susceptible to colds in fall and winter, but they can occur at any time of the year.


Being infected with the common cold can lead to the following complications:

Acute Bronchitis

This occurs when the bronchi (small tubes) in the lungs are inflamed as a result of either a bacterial or viral infection.

Antibiotics can only be used to treat this if the infection is bacterial; if it is viral, it is common just to treat the symptoms until the infection goes away with time since antibiotics do not effect a virus.

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