IV.

Viruses in Medicine

Viruses represent a major challenge to medical science in combating infectious diseases. Many cause diseases that are of major importance to humans and that are extraordinary in their diversity.

Included among viral diseases is the common cold, which affects millions of people every year. Recent research has even indicated that the AD-36 virus, which causes cold-like symptoms, affects food-energy absorption and more than doubles the normal layer of body fat in animals. About 30 per cent of obese people had contracted AD-36 compared with 5 per cent of lean people, and so this virus may contribute to obesity in a percentage of people. Other viral diseases are important because they are frequently fatal. These diseases include rabies, haemorrhagic fevers, encephalitis, poliomyelitis, and yellow fever. Most viruses, however, cause diseases that usually only create acute discomfort unless the patient develops serious complications from the virus or from a bacterial infection. Some of these diseases are influenza, measles, mumps, cold sores (also known as herpes simplex), chickenpox, shingles (also known as herpes zoster), respiratory diseases, acute diarrhoea, warts, and hepatitis. Still others, such as rubella (also known as German measles) virus and cytomegalovirus, may cause serious abnormalities or death in unborn infants. Acquired immune deficiency syndrome (AIDS) is caused by a retrovirus. Only two retroviruses are unequivocally linked with human cancers (see Leukaemia and HTLV), but some papilloma virus forms are suspected. Increasing evidence also indicates that other viruses may be involved in some types of cancer and in chronic diseases such as multiple sclerosis and other degenerative diseases. Some of the viruses take a long time to cause disease; kuru and Creutzfeldt-Jakob disease, both of which gradually destroy the brain, are slow virus diseases.

Viruses that cause important human disease are still being discovered. Most can be isolated and identified by laboratory methods, but these usually take several days to complete. One of the most recently discovered viruses is rotavirus, the causal agent of infant gastroenteritis.