Its most important job is protecting your body against foreign "invaders," such as bacteria and viruses.

The immune system is the body's defense against foreign substances, such as bacteria or viruses, that may be harmful.

Below these four classes are non-humans such as plants and viruses.

Pathogens (such as bacteria, viruses, and other germs) are too small to see.

Water can be contaminated from pathogens such as bacteria, viruses, and parasites.

Infectious agents such as viruses may also be present.

It only goes after microorganisms such as bacteria, viruses, and photomorphs.

Antibodies are part of the body's natural defences against germs such as viruses.

A small matter such as lethal viruses had not kept the humans away long.

In his view, children cannot understand abstract ideas such as viruses and diseases any earlier.