Explainer: What is a virus?

WASHINGTON — A virus is made of nucleic acids surrounded by a protein shell. There are many types of viruses; some like the coronavirus have RNA-based genetic material, while others contain a DNA-based genome.

According to the National Human Genome Research Institute, viruses straddle the definition of being living and nonliving. This is because viruses can only move or reproduce by infecting living cells, according to a study published in PubMed Central.

The PubMed study explains the human immune system can fight off viruses by deploying B-cells. These white blood cells produce antibodies that eradicate viruses before they get into cells.

The British Society of Immunology reports that another way the immune system fights viruses is to send killer T-cells to search and destroy infected cells. Since the immune response is attacking the body itself, it also causes stress to the patient.