Common cold causes

What causes the cold? How can I avoid it?

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Ask Dr. Jen Tan

Causes of a cold

Colds are caused by viruses. Scientists tell us that over 200 types of viruses are responsible for the cold.

The most common virus causing a cold is known as the rhinovirus (rhino means nose). More than 100 varieties of rhinoviruses exist. Other viruses causing colds include the coronavirus, adenovirus and respiratory syncytial virus.

As there are many families of viruses which cause colds, infections can be recurrent because immunity built up against one would not apply to the other 200 cold viruses. Or to put it another way - once you develop immunity to one, another virus may come along and cause a slightly different infection.

How do you catch a cold?

Colds are at their most contagious between two and four days after symptoms appear and someone affected can stay contagious for up to three weeks.

Colds are spread by viral particles in the air and spread by sneezing or coughing. You may catch a cold through close personal contact with one suffering the infection, by shaking hands or kissing. This used to be considered the most important cause of the cold.

However, we now know that it is possible to pick up a cold through indirect contact and research now suggests that this is the most common cause of a cold.

For example, if a person with a cold touches their nose or mouth, thousands of virus particles are transferred onto their skin. When they then touch an object such as a door handle, escalator rail, telephone or another similar object, virus particles are left behind. The next person to touch the object will pick up the virus, touch their nose or mouth and become infected.

Where are cold viruses found?

Cold virus particles can lurk in all sorts of places:

  • Computer mouse – around 45% of computer mice contain cold viruses and these may contain three times more ‘bugs’ than a toilet seat
  • Bank notes – a cold virus can linger on a used bank note for up to 17 days
  • Offices – around 40% of an average office, including desk surfaces, computer keyboards and telephones, is covered in cold and flu viruses. The office of a man contains more bugs than that of a female counterpart
  • Escalator rails – over 40% of escalator handrails have a high level of viral contamination
  • Petrol pumps – these are thought to have the highest level of bugs of all surfaces in public places.

How to avoid cold viruses

During the winter months, cold viruses can be rife so it will be impossible to avoid every single one of them. However, there are certain measures you can take to avoid exposure to these organisms:

  • Be careful what you touch – if you bear in mind how many germs accumulate on surfaces, you may be more careful about what you come into contact with. If you need to use the handrail on an escalator, cover your hand with a glove or your sleeve to prevent the viruses working their way onto your hands
  • Don’t share – well not everything. Germs like to nest on telephones and bugs can spread if you share cups or cutlery. Be particularly vigilant of what you share if the person is already infected by a cold virus
  • Wash your hands regularly – the easiest way for cold viruses to spread is via what you touch. Washing your hands regularly will stop viruses being transferred to your nose and mouth.

For more advice, read our tips on preventing colds and flu.

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