Viruses can cause virus diseases as diverse as measles, influenza, hepatitis, cold sores, chickenpox, glandular fever, the common cold, and AIDS. Viruses can actually infect the much larger bacteria, and this ability is used by scientists to introduce new genes into bacteria in genetic engineering.
The common cold can be caused by any one of several hundred different viruses. They cause the lining of the nose, sinuses and throat to become red, sore and swollen; and phlegm and mucus are produced in great quantities to give a stuffy head, sore throat and runny nose to their victim. The poisons created by the body destroying the viruses circulate around in the blood stream to cause the fever and muscular aches that are also associated with a cold. While the patient is suffering, the body is busy producing the appropriate antibodies to fight the infection. Once the number of antibodies produced is adequate to destroy most of the viruses, the symptoms of the disease disappear.
Doctors can vaccinate against some virus diseases, such as measles and influenza, to prevent them; but others such as the common cold cannot be prevented. Viral infections can best be avoided by a good, well-balanced diet, reasonable exercise, avoiding stress, avoiding extremes of temperature, and avoiding those who already have the infection.