Viruses depend on the genetic information found in the living cells in order to reproduce. As soon as they enter the host cell, they take over the cell processes and replicate the genetic information in order to reproduce copies of them.

The two patterns/paths of viral infection include the lytic infection and the lysogenic infection.

a. Lytic infection. This infection is characterized by the virus entering the cell and takes over the cell processes in order to reproduce itself right away.

b. Lysogenic infection. This infection occurs when the host cell is not taken over immediately. Instead, a viral nucleic acid is inserted into the DNA of the host cell and it stays with there for a long time until it is triggered by external factors such as heat, chemicals, and radiation.

The following diseases are caused by viruses:

1. Measles, rubella, and chickenpox are caused by exanthematous viruses, such as a varicella-zoster virus.

2. Chikungunya virus infection is caused by a Chikungunya virus that is transmitted to humans through a mosquito bite.

3. Rabies infection is a disease caused by the rabies virus, which is usually transmitted to humans through the saliva of infected animals.

Just like cells, viruses consist of a nucleic acid, which can either be DNA or RNA, that is enclosed by a protein coat. Once they were able to infect the host cells, they would have the ability to reproduce, to regulate gene expression, and to undergo evolution.

Viruses are considered as parasites since they are usually taking advantage of the infected host cells. During viral reproduction, viruses cannot undergo reproduction on their own so they borrow the abilities of the cells in order to reproduce themselves. Unlike viruses, cell-based organisms can reproduce on their own.

The graphic organizer below shows the comparison between viruses, prokaryotes, and eukaryotes.

The graphic organizer below shows the comparison between viruses, prokaryotes, and eukaryotes. (Click to see the graphic organizer)