CHECK-UPThere are many different types of viruses that cause infection and illness
What are viruses?
Viruses are small simple organisms that survive and multiply by invading other cells. In order to proliferate, a virus must first enter a living cell, reproduce and then, when the host cell dies, the new viruses are released, allowing them to spread and invade new cells.
There are many different types of viruses that cause infection and illness. Because viruses vary so much, the type of illness they produce and their severity vary greatly.
The common cold is caused by a virus. Other illnesses with a viral cause include influenza, cold sores, shingles and childhood diseases, such as chicken pox and mumps. Upper respiratory infections, pneumonia, bronchitis, gastroenteritis and meningitis can often - but not always - be caused by a virus.
Although many viruses can be overcome by the body's natural defences, more serious viral infections require close medical supervision and treatment with anti-viral and supportive treatment.
How do anti-viral drugs work?
There are several different types of anti-viral drugs and they work in different ways. Some anti-virals act by altering the cells' DNA ( genetic material) so that the virus cannot use it to multiply; other medications stop viruses reproducing by blocking the enzyme activity in the host cell; while another type prevents viruses entering the living cell in the first place and are therefore more effective if given before infection (prophylactically).
I keep getting cold sores around my mouth which I believe are caused by a virus. I use a cold-sore cream to clear them but they always return. Why doesn't the anti-viral cream destroy the virus?
Herpes simplex virus (HSV) causes recurrent episodes of painful, small, fluid-filled blisters on the skin or mucus membranes.
The recurrent nature of cold sores is due to the fact that between attacks the virus continues to live dormant in the nerve cells that supply the nerve fibres leading to the affected areas.
When the virus reactivates - as a result of stress, changes in hormone levels, physical trauma to the area, exposure to sunlight, illness or suppression of the immune system - the virus grows again, causing eruptions of blisters in the same area.
Topical or oral anti-viral drugs can help shorten the duration of the attack and can speed up healing but cannot destroy the virus itself.
Oral anti-viral drugs may be recommended for a prolonged period of time to help suppress reactivation of the virus.