Common Cold

A cold is probably the most common viral infection of humans. It has been estimated that adults suffer 2 to 5 colds per year and infants and pre-school children have an average of 4 to 8 colds per year.

Why are children more prone to catch a cold?

In children, the immune system may not have the kind of antibodies to combat the virus that causes the cold. But as people grow older, the immune system learns how to deal with more and more viruses as the body generates antibodies each time a person gets a cold.

Can a cold become a dangerous infection?

Infants, young children and the very elderly may develop secondary chest infections, which could be fatal. A person who is on medication, which depresses the immune system, may also be at risk.

From where does one get the infection?

Densely populated cities, heavily crowded transport systems provide an ideal breeding ground for the virus causing cold. Infection commonly occurs at home too. Young children with cold may become reservoirs for the viruses. Infection usually occurs at home or in the school. Adults with regular contact with children are most exposed to infection. It may be interesting to know that the start of school and college terms often coincides with an increased incidence of common cold infections and there is a decline in the incidence of infections during the summer vacations and half term periods.

How does common cold spread?

The viruses that cause cold replicate in the cells lining the nose and they are coughed or sneezed out in droplets of mucus. They are also spread by contaminated fingers, which pass the virus to the nose and eye. Tears from the eye drain via a duct into the nasal cavity and even when people touch their eyes with contaminated fingers, the virus passes into the nose!

When is a person most infective?

The incubation period for a common cold is usually around two days before symptoms start. People are most infective when the early symptoms of sneezing, runny nose and cough are present.

Can a chill cause a cold?

Cooling the skin and nose may cause sneezing and this maybe why we link a chill and colds. The air we breathe is colder in cold weather and this may cool the nose and allow the virus to replicate at a higher rate. There is no evidence that chilling the body causes an increased susceptibility to infection or an increase in the severity of symptoms.

Which viruses cause colds?

Over two hundred different viruses cause the symptoms of the common cold, but Rhinoviruses (nose viruses) account for approximately 30-40% of adult colds. Other viruses, such as coronavirus, respiratory syncytial virus, adenovirus, parainfluenza virus and influenza virus also cause the common cold. The nature of the virus cannot be identified from the symptoms, as these are very similar across the whole range of viruses.

What is a virus?

A Virus is a microbe that is much smaller than a bacterium, does not have a cell structure and is incapable of growth or reproduction, outside a living cell. For example, the Rhinovirus that causes cold is about 20 nanometers in diameter. To understand that size one can imagine 50,000 rhinoviruses lined up across one millimeter.

How exactly does the virus cause an infection?

The common cold virus or rhinovirus has special provisions to fit on to a portion of the cell in the nasal cavity. It is almost like a docking port. Once attached to the cell the virus enters the cell and uncoats to release its strand of genetic code. This code is in the form of RNA (Ribo Nucleic Acid) and is rather like a bit of computer code which is inserted into the cell machinery and which instructs the cell to construct new viruses. The strand of RNA contains around seven thousand nucleotides and is in the form of a long string, which is tightly coiled inside the viral shell. The viral RNA switches off the normal operation of the cell and the cell produces thousands of copies of the virus. The viruses are released into the nose when the cell disrupts. These viruses soon infect adjacent nasal epithelial cells or are expelled from the nose in drops of mucus to start a new cycle of infection in another human nose.

What is the 'Iceberg Concept of Infection?'

Most viral infections in humans produce no disease at all. They do not produce any symptoms, despite extensive viral replication. The majority of viral infections pass unnoticed without any signs of disease and this is known as the 'iceberg concept of infection.' That is, the classical and severe disease cases, which are presented to a doctor, only represent the tip of the iceberg of infection.

What is the relationship between stress and the common cold?

The stress of every day life can influence the susceptibility to infection. Experimental studies in which common cold viruses have been administered into the nose of healthy volunteers have shown that there is a link between recent history of psychological stress and susceptibility to infection. Stress could suppress the general resistance of a person to infection. It is said that psychological stress may affect the immune system by increasing the release of corticosteroid hormones, which are known to decrease resistance to infection.

Can a person who has just recovered from a cold get infected again?

Viral infection triggers the immune response by the activation of white cells, which act as killer cells or produce specific antibodies. It is the killer cells, which overcomes the infection rather than the production of antibodies. Antibody production starts two weeks or so after the infection and reaches a maximum after three to four weeks. The antibodies help to prevent repeat infections by the same virus but do not protect against other viruses. Since there are over two hundred different types of cold virus, a person who has just recovered from a cold could be infected again by another type of virus.

What triggers the symptoms?

Natural disinfectants are produced by the white cells as part of the inflammatory and immune response to viral infection. These lead to the generation of chemical mediators such as bradykinin, prostaglandins, tachykinins, histamine and cytokines. These mediators act on the blood vessels, glands and nervous tissue, causing the symptoms of common cold.

Why is Bradykinin being talked about?

Bradykinin is said to play a major role in producing the symptoms of cold. It has been detected in nasal washings taken from patients with common cold infections. Intranasal administration of bradykinin in healthy volunteers causes, nasal congestion, nasal irritation, throat irritation and stimulation of nasal secretion. Research is being done to develop a medication, which would act as a bradykinin antagonist as this could be used to treat the symptoms of common cold, just like antihistamines are used to treat symptoms of allergy. Bradykinin is also implicated in causing the pain and swelling associated with joint inflammation in Rheumatoid Arthritis.

What are the symptoms of common cold?

A dry sore throat is often the first sign of a common cold and this may be due to the virus first infecting the back of the nose. Sneezing and a clear watery nasal discharge may also be present in the early stages of infection. Symptoms usually last for about 7 days, although they may persist for up to 14 days. Fever associated with common cold is uncommon in adults but quite common in infants and children.

How does the nose get blocked?

The swelling of large veins lining the nasal passages causes nasal congestion.

Why is cough associated with a common cold, which is a nasal infection?

Inflammation and infection of the larynx, trachea and lower airways in a person with common cold, causes a dry non-productive cough.

Tips on preventing a cold:

Wash your hands often. Keep them away from your nose, eyes, and mouth. Try not to come into very close contact with people when they have a cold, especially the first 2-3 days they have the cold. This is the most contagious stage. Get lots of exercise. Eat and sleep well. Use a handkerchief or tissues when you sneeze, cough, or blow your nose. This helps keep you from passing cold viruses to others.

Time is the only cure for a cold. Here are some tips to make a person feel better:

Rest in bed if you have a fever. Drink plenty of liquids. They help clear out your respiratory tract. This can help prevent other problems, like bronchitis. Take an over-the-counter medicine for muscle aches and pains or fever. Use salt-water drops to relieve nasal congestion. Mix 1/2 teaspoon of salt in 1 cup of warm water. Place in a clean container. Put 3 to 4 drops into each nostril several times a day with a clean medicine dropper. If a child has difficulty in breathing due to nasal congestion, it may help to raise the head with a blanket. Check with your doctor before trying vitamin C. It seems to make some people feel better when they have a cold and may help keep them from getting a cold, even though this has never been medically proven.

Tips to take care of a sore throat:

Gargle every few hours with a solution of 1/4 teaspoon of salt dissolved in 1/2 cup of warm water. Drink tea with lemon. Suck on medicated lozenge lemon drops to relieve the symptoms of a dry throat. Medicated lozenges may not be advisable for children under age 5.