What are antiviral drugs and how do they work? - The New York Times

Antiviral medications have been around since the 1960s in the form of pills, intravenous solutions, ointments and even eye drops. They exist for only a handful of viruses, including H.I.V., the herpes simplex viruses, hepatitis B and C viruses, influenza A and B, and now the coronavirus.

Tamiflu, one of the most well-known antivirals, can minimize flu symptoms and shorten the course of illness when taken within a few days of getting sick. It can also be used prophylactically (in nursing home residents, for example) to prevent viral spread during outbreaks. Other antiviral therapies, like those for H.I.V. and hepatitis C, can be taken chronically, even in the absence of symptoms, to prevent the disease from progressing and to curtail symptom flares.

Most antivirals work by suppressing a virus's ability to infect and multiply in your cells, said Dr. Rajesh Gandhi, an infectious diseases physician at Massachusetts General Hospital. This helps the body fight off an active infection by easing the symptoms and shortening the length of the illness.

But the exact way an antiviral does this depends on the treatment you use. Some antivirals prevent viruses from spreading to healthy cells by blocking the receptors on cell surfaces. Others inhibit the machinery that a virus needs to make copies of itself once it has already barged inside your cells. Because of this, it has been notoriously difficult for researchers to develop antiviral medicines that blunt viral replication without harming the human cells they hide inside, Dr. Gandhi said.