health

Viruses can enter the human body through any of its openings, but most
often they use the nose and mouth. Once inside, the virus attaches itself
to the outside of the kind of cell it attacks, called a host cell. For example,
a rhinovirus attacks cells in the nose, whereas an enterovirus binds to cells
in the stomach and intestines. Then the virus works its way through the
host cell’s outer membrane.
After entering the cell, the virus begins making identical viruses from
the host cell’s protein. These new viruses may make their way back out
through the host cell’s membrane, sometimes destroying the cell, and then
attacking new host cells. This process continues until the body develops
enough antibodies* and other defenses to defeat the viral invaders.
Not all viruses attack only one part of the body, causing what is called
a localized infection. Some viruses spread through the bloodstream or
the nerves, attacking cells throughout the body. For instance, HIV*, the
human immunodeficiency virus that causes AIDS*, attacks certain cells
of the immune system that are located throughout the body.