Everybody knows by now that the United States and the world are in the grip of one of the dangerous coronaviruses called COVID-19, but what’s a virus and how can it make us feel ill? Why do our bodies react the way they do? Are viruses alive?

“Viruses aren’t considered alive – in class I call them pseudo-alive,” says Dr. Eric Mendenhall, an associate professor of biological sciences at The University of Alabama in Huntsville (UAH).

A virus has got to have a living cell before things can rock and roll.

“They require a host to even begin to function. However, since they use DNA or RNA to pass information to the next round of viruses the cell makes for them, they are subject to some of the same principles of evolution and selection that alive organisms are subject to,” Dr. Mendenhall says.