The virus infections happens when a virus gets past the physical barriers of the body (skin, mucus, and so on) and infect a suitable cell, the virus take the genetic machinery of the host cell to replicate, damaging that cell and making more virus that will do the same process with other suitable cells. After the virus use all the cell potential, it will kill the cell and release all the virus that were in the cytoplasm of the host. While bacterial infections have more autonomy, being not necessary the integral machinery of the cell to multiply in the host body, it can act in differrebt ways, such as: crowd out the host tissue and disrupt the function, killing the cells or tissues outright, destroy the metabolic machinery, cause a massive toxic reaction in the immune system, and release toxins that can make the body stop all their functions at once (paralyze the metabolic and general system of the host).