A virus is a nonliving entity that can cause infections. They infest specific cells in the host, killing them and reproducing more viruses. They are contagious, but it requires more effort for them to transmit. They also are unaffected by antibiotics. Antivirals do get them as does a functional immune system. Bacteria (living cells) can be killed with antibiotics and are more easy to spread but also a little easier to combat. However, they have different ways of causing illness in people depending on where they are. Quite a few are beneficial. Antibiotics don't discriminate as well as one would hope though.
Viruses are not contagious.. Bacteria is..
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