virus

A virus is an ultramicroscopic agent that can only reproduce in living cells and is spread through infection. Many viruses cause diseases as part of their reproduction process.

Viruses are only 20 to 300 nanometers—so small that even microscopes can’t see them. Viruses are also very simple. They consist of a core made of DNA or RNA, a protein coat that surrounds the core, and sometimes an envelope that surrounds the core.

A virus can’t reproduce on its own. Instead, it will infect a living cell and force it to make more copies of the virus. When the virus does this, it stops the cell from whatever it was doing before and, eventually, kills the cell.

Viruses are infectious, meaning they often cause symptoms that allow fluids with copies of the virus to spread to other organisms. For example, if you have the flu and cough on another person, your virus-containing saliva and mucus will enter the other person’s body and allow the virus to infect their cells.

Because viruses remain inside living cells, it is often impossible to kill the virus without also killing the cell. Usually, your immune system is the only thing that can safely fight a virus.

Viruses are responsible for some of the most deadly, incurable diseases we have today. In 2019, a new type of coronavirus (a family of viruses that often cause respiratory illnesses) was the cause of a deadly disease known COVID-19 (short for coronavirus disease 2019), which became a worldwide pandemic.

Viruses have also been responsible for other serious diseases, such as HIV (short for human immunodeficiency virus), that causes AIDS, a disease in which the immune system gradually breaks down and often leads to cancer.

Because viruses are so hard to kill and some can make you very sick, we try to prevent viruses from infecting us in the first place. Washing your hands, not breathing on people, and staying home when you are sick with a virus all help prevent the virus from spreading.

Vaccines are used to train your immune system to better fight specific viruses. Sometimes, antiviral medications can interfere with the virus’s ability to take over a cell or treat the symptoms of the virus rather than attack the virus itself.

The word virus is also used to describe malicious computer code that is designed to harm or infect computers in a similar way to how a biological virus infects living things.

This photo depicts an image of a virus.

National Geographic / Maryna Olyak

Viruses cause many deadly diseases so people are never fans of them.

Q: Which antibiotic should you take to treat COVID at home?

Azithromycin
Levofloxacin
Doxycycline
Augmentin

A: None

Antibiotics kill bacteria; COVID is caused by a virus

Unnecessary antibiotics and/or steroids in non-hospitalized patients do more harm than good

— Faheem Younus, MD (@FaheemYounus) July 15, 2020

I swear every time I leave the house I pick up a new virus

— Pilgerz (@EveLily95) January 6, 2018

• HIV
• AIDS
• COVID-19
• smallpox
• measles
• rabies
• influenza

True or False?

Because viruses are hard to kill, we try to prevent them from spreading in the first place.