A virus is defined as any of a various number of submicroscopic parasites that can infect any animal, plant or bacteria and often lead to very serious or even deadly diseases. A virus consists of a core of RNA or DNA, generally surrounded by a protein, lipid or glycoprotein coat, or some combination of the three. No virus can replicate without the help of a host cell, and though they can be spread, viruses lack the ability of self-reproduction and are not always considered to be living organisms in the regular sense.
Some of the most common or best known viruses include the human immunodeficiency virus (HIV), which is the virus that causes AIDS, the herpes simplex virus, which causes cold sores, smallpox, multiple sclerosis, and the human papilloma virus, now believed to be a leading cause of cervical cancer in adult women. The common human cold is also caused by a virus.
Since a great deal of mystery still surrounds the origins of most modern viruses, ways to cure these viruses and the diseases they cause are still in the very early stages of development.
In October 2010, the body of a young short-beaked common dolphin was found stranded on a beach in San Diego. The sickly female had lesions in its airway and a necropsy showed that it died of tracheal bronchitis, likely caused by an infection.
It's well known that chronic diseases such as obesity, type 2 diabetes and heart disease can be prevented in many cases by eating well, exercising and avoiding smoking. So why do so many of us have a difficult time we doing these things?