Viruses

Viruses are defined as microscopic particles (30 t0 300nm; 1nm = 10-9 ) containing DNA or RNA. within a cover of protein. A bacteria is 100 times bigger than this. They cannot be
seen through a light microscope.

Viral Diseases.

All varieties of flu and  poxes, raging from chicken pox to small pox and such terrible diseases as polio, rabies and AIDS are caused by viruses. Dengue and Chickengunya are acute viral diseases transmitted by the mosquito Aedes Aegypti. There are many varieties of the same disease, so an infection of one type will not produce immunity for others. That’s how we get flu so many times.

Dengue starts off with a headache and soon, fever, muscular aches and joint pains arise and rashes appear. There may also be abdominal pain nausea and diarrhoea.  The disease is not directly infectious. At the end of the fever platelet count drops. Platelets are the cell fragments circulating in the blood that are involved in the repair of blood leaks from the capillaries . So a low platelet count will lead to internal bleeding.

The latest is the Ebola virus.

Viruses gain entry into living cells and use up the cell contents to make its own type of living matter. Then they multiply and escape to infect more living cells of the host. Some viruses readily attack bacteria. They are known as bacteriophages.

Treatment for Viral Attacks

In case of a bacterial infection, your doctor can prescribe anti biotics. What can he give for a viral attack? He’ll say “ Viruses are not biotic; anti-biotics wont do.” In the 18th Century Mary Montague , an English lady observed in Constantinople, local women blowing small pox crusts into  the nostrils of their children. This process came to be known as ‘inoculation’. Edward Jenner observed Miss Sarah Nelmes , a milk maid who had previously caught cow-pox was immune to small-pox. Even today  the only way to fight viruses is to build up immunity. When a person gets a viral attack the body makes anti-bodies which can counteract the invader. This is why we normally don’t get the same infection twice.

Are they Living

There is no definite answer to this. It all depends on how you define life. Viruses do not have cells. They only contain nucleic acid, (DNA, RNA) which are capable of carrying out physiological functions only  inside a host  cell. A plus factor for the argument is that they are capable of making copies of their type of nucleic acid.Viruses are not the only dwellers between the living and the non living. There are the PRIONS, (Proteinaceous Infectious Particles)   that lack nucleic acid. When these gain entry into the living cells they behave just like viruses. Viroids are another group that cause disease in plants. They consist of a strand of RNA only.

Origin
One hypothesis is that they have undergone reverse evolution due to a parasitic way of life. Cells and some of the contents may have degenerated as they were not being used.
Another view is that they may have been formed by some run away parts of nucleic acid which have got detached from the genes of higher animals and plants.
A third possibility is that they were the pioneers of life.

Comparing Microbes

   Bacteriophages are also a group viruses that attack bacteria. click: bacteriophages