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Villain. Killer. Menace. Since 2020, scientists and public officials have used these words to describe SARS-CoV-2, the virus that causes COVID-19. News articles, research papers and tweets repeatedly personify the virus as a bad guy intent on killing us.

Simultaneously, we’re intent on killing it, with handwashing, antiseptic wipes, hand sanitizer, bleach, even robots zapping hospital rooms with ultraviolet light. Yet, according to most scientists, we’ve been working hard to kill something that isn’t alive.

Scientists have argued for hundreds of years over how to classify viruses, says Luis Villarreal, professor emeritus at the University of California, Irvine, where he founded the Center for Virus Research. In the 1700s, viruses were believed to be poisons. In the 1800s, they were called biological particles. By the early 1900s, they’d been demoted to inert chemicals.

Throughout, viruses have rarely been considered alive. More than 120 definitions of life exist today, and most require metabolism, a set of chemical reactions that produce energy. Viruses do not metabolize. They also don’t fit some other common criteria. They do not have cells. They cannot reproduce independently. Viruses are inert packages of DNA or RNA that cannot replicate without a host cell. A coronavirus, for example, is a nanoscale sphere made up of genes wrapped in a fatty coat and bedecked in spike proteins.

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