Virus (or viruses) are microscopic organisms that can infect hosts, like humans, plants or animals. They’re a small piece of genetic information (DNA or RNA) inside of a protective shell (capsid). Some viruses also have an envelope. Viruses can’t reproduce without a host. Some common diseases caused by viruses include the flu, the common cold and COVID-19.
What are the types of viruses?
Experts group virus 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.
- Human papillomaviruses.
- Hepatitis viruses.
There are also some viruses that have unique qualities, like retroviruses and oncoviruses.