I think it’s high time that we understand what a virus is. I say this as i have read news regarding corona virus infected people being irresponsible and basically being foolish and running around when they are asked to stay isolated. Like really, how foolish can you be. Why cant people understand a simple request . When you are asked to stay inside because of being infected,do it.

Ok , so lets understand a Virus

Viruses are small infection causing agents that only replicate inside a living cell. When not infectinga cell, they exist freely in the environment as virions and consist of

  1. genetic material: DNA or RNA
  2. protein coat, the  capsid , which surrounds and protects the genetic material
  3. and in some cases an outside envelope of lipids

Viruses vary in shapes from helical , icosahedral to complex ones. These virions are so small (about one virushundredth the size of bacteria that it cannot be viewed under an optical microscope. although their evolution is not clear, their are millions of types of viruses around the globe.

Viruses spread in many ways.

vectors: for example, viruses are often transmitted from plant to plant by insects that feed on plant sap, such as aphids; and viruses in animals can be carried by blood-sucking insects. Influenza viruses are spread by coughing and sneezing. Norovirus and rotavirus, common causes of viral gastroenteritis, are transmitted by the faecal–oral route, passed by contact and entering the body in food or water. HIV is one of several viruses transmitted through sexual contact and by exposure to infected blood.

The variety of host cells that a virus can infect is called its “host range“. This can be narrow, meaning a virus is capable of infecting few species, or broad, meaning it is capable of infecting many.Viruses can be the cause of common infections such as flu, common cold, warts and also deadly infections such as Ebola, Nipah, AIDS.

Viral infections can affect many parts of the body  the brain, liver ,skin reproductive, respiratory etc. It depends on the type of virus you are being infected with.



A viral infection means proliferation of virus inside a human body. Viruses can replicate inside a living cell by hijacking the cells internal machinery and utilizing it to create more viral copies. The virus at the end either burst opens the cell and releases the virions to infect the nearby cells or it buds off the host cell over  a period before killing it.

A viral infection is contagious and it depends on the virus you are being infected with.  An incubation period of a virus varies from its contagious period. An incubation period is the time from when you are first exposed to the virus to the time your first symptoms arise.

Let’s cover some common types of viral infections

  1. Respiratory viral infection

Rhinovirus virus, Seasonal influenza , Corona virus (CoVid19) are all examples of respiratory viral infections. Symptoms include sneezing, coughing, headache sore throat etc. These are common symptoms of any respiratory infection but it does vary with the type of infection. Like In flu the symptoms are more intense than in  common cold and in Corona virus infection the symptoms prominently are fever, cough and difficulty breathing.

Frequent hand-washing, covering the nose and mouth when coughing or sneezing, and avoiding contact with infected individuals can all reduce the spread of respiratory infections. Disinfecting hard surfaces and not touching the eyes, nose, and mouth can help reduce transmission as well.

2. Viral skin infections

Molluscum contagiosum,Herpes simplex virus-1 (HSV-1) are some common skin infections. The best way to avoid viral skin infections is to avoid skin-to-skin contact (especially areas that have a rash or sores) with an infected individual. Some viral skin infections, such as varicella-zoster virus( causing chicken pox), are also transmitted by an airborne route. Communal showers, swimming pools, and contaminated towels can also potentially harbor certain viruses.

3. Food borne viral infections
 Noravirus, Rotravirus are all food borne viral infections that are transmitted through  fecal-oral route These are also known as viral gastroenteritis, which causes inflammation of the stomach and intestines. to prevent such infections hygeine is very important . The very basic habit of washing your hands can help you from not being infected.

 There are many kinds of viral infection like the sexually transmitted ones(Hepatitis B, HIV/AIDS) and others, for example Viral meningitis, West Nile Virus ( transmitted by mosquitos).

Viruses reproduce creating virions in the process using lytic or lysogenic process .

Viruses opting for lytic cycle penetrate the cells , divide in it , release the virions by bursting open the cell and killing it whereas a lysogenic cycle involves the viral DNA integrating into the host cell genome and then creating virions which are released by budding from the host cell surface. This viral cycle doesn’t kill the cell at first but eventually the virus will enter the lytic cycle of reproduction and kill the host cells.

Lets move on to a pictorial mode of learning.

  1. These are the normal steps involved in the reproduction cycle of a virus

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2. Once the viral genetic material is injected into the host cells it is replicated , transcribed and translated to create virions.     

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3.The viruses follow either the lytic cycle ( where they destroy the cells they replicate in ) OR


Lytic cycle in a bacteriophage

4. The lysogenic cycle which invoves the integration of the virus genetic material into the host genome. The virus continues inthe lysogenic phase but ultimately switches to the lytic phase when prophage ( phage DNA integrated into the host DNA) is exposed to stressors, such as UV light, low nutrient conditions, or chemicals like mitomycin C, prophage may spontaneously extract themselves from the host genome and enter the lytic cycle in a process called induction.

Lysogenic cycle in a bacteriophage

Image credit


Viruses have been around for many decades, still we have not developed a mechanism to counter them. Another problem is that we still don’t feel the need to understand its seriousness as an infecting agent. The number of deaths an infection causes should not be the rating scale for its seriousness. When a disease can be stopped spreading by awareness, washing our hands and following a good hygeine why is so difficult to follow. Why is it that we need to link it with bizarre activities like people gathering to sing “Corona virus to away” , when the first guideline by health authorities is to avoid public gatherings. Simple hygienic habits like not spiting on the road, washing your hands, avoid touching your mouth, nose areas and keeping distance from an infected person can save you.



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6 thoughts on “VIRUS”

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