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.
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:
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.
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.
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:
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.
A sample of the sputum may be taken and examined under a microscope to determine what the levels of bacteria are. Symptoms include wheezing, shortness of breath, coughing, and sputum.
This is another condition where the lungs are inflamed, but this time, it is due to the alveoli (tiny air sacs) filling with fluid.
Pneumonia can be caused by bacteria or viruses. However, the common cold virus does not cause pneumonia. If pneumonia occurs as a complication of a cold, it is most likely to be bacterial. Antibiotics may be prescribed. Symptoms include chest pain, cough, fever, and breathing difficulties.
Acute Bacterial Sinusitis
This is when bacteria infect the sinuses. Nasal and oral decongestants can be used to manage symptoms; however, antibiotics are required to treat the condition and to prevent further infection, which could lead to other conditions, such as bacterial meningitis in rare cases.
Symptoms include headache, aching sinuses, and nasal discharge.
Other complications of the common cold include:
People with the following conditions can be vulnerable to the common cold:
Chronic obstructive pulmonary disease (COPD) - this includes both emphysema and chronic bronchitis. The common cold can exacerbate emphysema or chronic bronchitis symptoms, leading to increased coughing and shortness of breath. Sometimes, a bacterial infection can occur which leads to fever; antibiotics may be prescribed.
Asthma - asthma attacks can be triggered by a cold, especially in children.
As there are so many viruses that can cause a cold, it is difficult to develop a vaccine.
However, there are some precautions that can help avoid catching the common cold. These include:
- Avoid close contact with someone infected with a cold.
- Eat plenty of vitamin-rich fruit and vegetables to help keep the immune system strong.
- When sneezing or coughing, make sure it is done into a tissue. Discard the tissue carefully and wash your hands.
- If you sneeze into your hands, make sure you wash them with soap and water immediately.
- If you have no tissues or a handkerchief, cough into the inside (crook) of your elbow rather than your hands.
- Wash your hands regularly; cold viruses can be transmitted from one person to another by touch. In fact, more germs are passed by shaking hands than by kissing.
- Keep surfaces in your home clean — especially in the kitchen or bathroom.
- Avoid touching your face, especially your nose and mouth.
It is important to realize that both antibiotics and antiviral medications are ineffective against most viruses that cause the common cold. A cold normally lasts up to 10 days; however, some symptoms can stay as long as 3 weeks.
Although there is no real way of treating or curing a common cold, the following measures may help ease the symptoms:
- Drink plenty of fluids and keep well hydrated, being dehydrated when infected with a cold can make symptoms worse.
- Get plenty of bed rest; it is important to get as much sleep/rest as possible while the immune system is fighting off the virus.
- Take aspirin, acetaminophen, or ibuprofen to relieve headache or fever. Do not give aspirin to children under 16.
- Some people find that inhaling steam helps ease the symptoms of nasal congestion.
Find out more about how to treat and manage a cold: How to treat a cold.
As symptoms can sometimes be quite similar, it may be difficult to know whether you have the flu or a bad cold. Generally, flu symptoms are felt sooner than cold symptoms. Flu symptoms are also more intense. People with the flu feel weak and tired for up to 2–3 weeks. As the fever comes and goes, there will be periods of chills and sweats (cold sweats). Their muscles will ache, and they will have a runny or bunged-up nose, headache, and sore throat.
Treatment is often with antivirals. Immunization (flu shot, or flu mist) is available to aid in prevention. Please see "Flu: Causes, symptoms and treatments" for further information.
Cold versus flu symptoms
The following symptoms are common with flu but not always with a cold.
- Headache: Uncommon in cold but possible. More likely in flu.
- Tiredness and weakness: Occasionally, but milder than with flu.
- Extreme tiredness: Uncommon.
- Aches and pains: Much milder than with flu.
- Temperature/Fever: Unusual, generally higher fevers with flu.
- Sneezing: A common cold symptom.
- Stuffed up or runny nose: Quite common.
- Coughing: Occasionally, but not as severe as with flu.
- Dry or sore throat: Common.
Treatment only provides temporary relief of symptoms, and good hygiene is the best prevention.