The viral genome has 4 genes only. One of them code for the coat protein, two for replicase enzyme and the fourth for a protein that probably enables

• The viral genome has 4 genes only. One of them code for the coat protein, two for replicase enzyme and the fourth for a protein that probably enables the virus to spread from cell to cell in the plant.
• Viruses are not affected by antibiotics
• Till date, viruses could not be cultured in any type of culture medium in the laboratory.
• The smallest virus (causing foot and mouth disease in cattle) measures about 20 milimicrons and is about the size of largest protein molecules. The largest virs measures about 350 nm and is as large as the smallest bacteria
• Tobacco mosaic virus is the first documented virus
• An unknown respiratory fatal disease had shaken the world in 2003. it was named SARS and is caused by a virus. It became an epidemic. From Nov. 2002 to July 2003, there were 8096 known cases of the disease and 774 deaths across the world which sums up to a mortality rate of 9.6%.
• Epidermics of smallpox had inflicted mankind throughout history, and as recently as 1967, some 10-15 million cases were still occurring annually in more than 30 countries on January 1 1967, the world Health Organization launched the intessified Smallpox Eradication programme. In India, Operation smallpox zero was launched in 1977, the last case of smallpox was reported in Somalia. For the first time a major disease has been completely vanquished.
• It is a virial disease. The virus causing smallpox is preserved in two high security laboratories in Atlanta and Moscow. Human population of today does not have antibodies for smallpox in their body . so an outbreak would be a major devastation now.
• The avian flu or bird flu that was an epidemic of poultry fowls in the year 2003 is caused by a special influenza virus named H5N1.