• Viruses are microorganisms that are smaller than bacteria and cannot grow or reproduce outside of a living cell.
• Viruses invade living cells and use the cells’ substances to survive and replicate.
• Viruses consist of genetic material (DNA or RNA) and a protein shell. They may reproduce by making a perfect copy, or copies with errors (mutations); this ability to mutate is the reason why some viruses are able to change slightly in each infected person, making treatment difficult.
• Viruses are the cause of many common infections and are also responsible for a number of rare diseases.
• A milder form of viral infection is the common cold (usually caused by rhinoviruses), flu is a moderate condition, some serious illnesses caused by viruses are hepatitis and conditions caused by the human papilloma virus (HPV), and one of the most complex diseases caused by viruses is AIDS (acquired immunodeficiency syndrome), which is invoked by HIV (human immunodeficiency virus).

Types of viruses
Common colds are mostly caused by rhinoviruses, but coronaviruses, adenoviruses and respiratory syncytial virus (RSV) can also contribute.

Spread
Viruses are spread by airborne droplets via the infected coughing, sneezing or talking.

Symptoms
The most common symptoms are sore throat, cough, nasal congestion, sneezing, headache and general weakness.

Incubation period
Cold viruses typically have an incubation period of 1 to 3 days.

Treatment
Painkillers, nasal sprays or lozenges that work against viruses and moisturise the nasal mucosa.

Prevention
It is important to maintain hygiene, wash your hands frequently, and avoid contact with infected people.

A short video on how a virus invades your body.

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