1.Not Alive but Not Dead Either
Viruses are said not be living organisms because they have no cells and cannot convert food into energy. If they have no host, they are mere inert chemical packets. However, viruses are not completely dead organisms because they have genes that enable them to reproduce and evolve via natural selection.

 2.Debated for more than a Century
Viruses have been debated by scientists since 1892. A Russian microbiologist, Dmitry Ivanovsky discovered an infection that spread in tobacco crops through something much tinnier than bacterium. The tiny something was later named the tobacco mosaic virus. This discovery triggered the debate that has ranged to date.

 3.Purification of Tobacco Mosaic Virus
Wendell Stanley, a biochemist of American descent purified the virus in tobacco crop into crystals of protein that resemble needles. He won the Nobel Prize for this achievement in 1964 in chemistry and not in medicine.

 4.Meaning of the Term Virus
The term virus is derived from the Latin word that means slimy liquid or poison. It is an apt description of a bug that causes common cold and flu. Some viruses are known to get sneak their DNA into bacterium through their um, long tube sex appendage called pilus. Scientists who were tracking an outbreak of pneumonia in England in 1992 came across a huge virus type lurking in an amoeba. The virus was so complex and large that the scientists assumed that it was a bacterium.

 5.The Largest Viruses
One of the largest viruses known are the mimiviruses that measure 0.0004 millimeters in diameter. Their viral genome has a length of 1,200,000 nucleotides and codes for more than 900 proteins. These codes encode proteins that other viruses do not have. The genome in mimiviruses is two times bigger than that of other known viruses as well as that of most bacteria. Mamaviruses, which are related to Mimiviruses are bigger than mimiviruses to an extent that they have a satellite, dependent virus called Sputnik.

 6.Breeding Places for Viruses
Amoebas happen to be great places where new viruses form. Since they swallow huge things, amoebas serve as mixing bowls where bacteria and viruses swap genes. The tinniest viruses are known as circoviruses. They measure 0.00002 millimeters in diameter and have a viral genome of 1700 nucleotides long and two-code proteins.

 7.Viruses Infect Living Things
Viruses tend to infect plants, animals, protozoa, fungi, bacteria and archea. Mamavirus and Sputnik show that they are capable of infecting other viruses as well. The first virus infection on human beings was the yellow fever virus. It was discovered by Walter Reed in 1901.

 8.Genetic Combination of Viruses
Viruses are either RNA or DNA. They occur in a single molecule or in several pieces and can either have a single strand or multiple strands. Though viruses are commonly known to cause diseases, some viral relics in human genomes play an important part in autoimmune certain cancers and diseases. Some viral proteins are known to stop immune systems in pregnant mothers from attacking the fetus.

 9.Sea Water is Laden with Viruses
Each milliliter of water found in seas and oceans contains approximately one million virus particles. This gives a global total of about 10³⁰ virions. If lined up one after another, end to end, the viruses would stretch into space up to 200 million light years.

 10.HIV Genomes
More than 10¹⁶ HIV genomes are generated each day across the world. This leads to thousands of viral mutants that are resistant to each antiviral compounds arising each day.