Viral Sickness Viruses do not require food to eat and do not produce any waste. They even don’t respire like other living beings. They represent the smallest forms of life and act as the connecting link between the living and the nonliving. The only living characteristic they show is reproduction in the body of the host with the help of the host’s DNA machinery. Once inside the host, viruses multiply and produce disease. It may appear that they are not alive because they do not respire, but they are considered to be living organisms because they can reproduce. Structure of a Virus A virus consists of two basic parts. An outer protective wall is made up of proteins called capsid, which protect the virus against harsh environments for many years. Inside this protective coat is its DNA, which reproduces with the help of the host DNA synthesis machinery.

Virus particle


4. Assembly and packaging

1. Attachment (adsorption)

Cell (host)

Protein coat remains outside

Viral DNA enters

2. Penetration (injection)

5. Release (lysis)

Mature virus particles

3. Synthesis of nucleic acid and protein


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