VIRUSES

A virus is a small piece of genetic information in a “carrying case” — a protective coating called a capsid. Viruses aren’t made up of cells, so they don’t have all the equipment that cells do to make more copies of themselves. Instead, they carry instructions with them and use a host cell’s equipment to make more copies of the virus.

It’s like someone breaking into your house to use your kitchen. The virus brought its own recipe, but it needs to use your dishes, measuring cups, mixer and oven to make it. (Unfortunately, they usually leave a big mess when you finally kick them out.)

Viruses are also sometimes called “virions.”

Virus features

Viruses share some common features. Viruses:

• Are made up of genetic material (RNA or DNA) and a protective protein coating (capsid).

• Sometimes have another layer called an envelope around the capsid. Viruses without an envelope are called “naked viruses.”

• Are similar to parasites — they need a host to reproduce. They’ll survive outside of a host until their capsid breaks down over time.

• Are 100 to 1,000 times smaller than the cells in your body.

What are the types of viruses?

Experts group viruses into categories — like family and genus — based on similar features, like size, shape and the type of genetic material they carry. Some common types of viruses that you might hear about include:

• Influenza viruses.

• Human herpesviruses.

• Coronavirus.

• Human papillomaviruses.

• Enteroviruses.

• Flaviviruses.

• Orthopoxviruses.

• Hepatitis viruses.

There are also some viruses that have unique qualities, like retroviruses and oncoviruses.

STRUCTURE OF VIRUSES