Covid-19 is not completely over in the world.so many people are died,critical in situation.in this time we have somany questions covid -19 is only a virus? What is meant by virus?how to effect?etc.

Viruses are microscopic particle are found in plants and animals body , and other organisms.they can sometime cause .

Viruses are biolagical entities that can only thrive and multiply in a host . which is a living organism that living organism such as an human and plants.

Virus may also effect one organism in one way but different one in another.this explain why a virus that illness in a cat may not effect a human.

Virus vary in a form and complexity they consist genetic material such as DNA and RNA ,with a coat of protein around it,some have additional coat is called envelope.this may be spiky and helps them latch onto and enter host cell.they can only replicate in a host.

WHAT ARE VIRUS?

Virus are microscopic entities that have a core of a genetic material.genitic materials are DNA or RNA .That covered by a capsid made up of protein.

They also do not containe ribosomes,so they cannot make protein.it is the reason for virus are without living a host.They make unable reproduce independly and totally Dependant on the host . 

After entering a host cell they hijack cell by releasing  iits own genetic material and protein in to the host.it uses the host cellular machinery to make many copies it self.

Next they continue to reproduce but it produce more protein and genetic material instead the usual product that cell produce.

Virus has different shape and size .rod shape ,almost spherical shape .they contain a nucleic acid they can determine the genetic shape of the virus.

Example of virus that can influence a coat or envelope in HIV and influenza. With these categories different types of viruses .A corona virus for example that has spherical In shape helical caps I'd .that contain RNA it also envelope crown like spike on its surface .seven corona virus that can effect human body but each one change or u mutate or producing mutate variant.

HARMLESS VIRUS'S

Just as there friendly bacteria in the intestine that are essential to gut health of human body .human may also carry friendly viruses help protect.

SOURCES

Virus do not leave fossil remain,so they are difficult to trace through time.secintist use molecular technique to compare the DNA and RNA of viruses and find out more about where they come.