Antiviral

An antiviral is a substance that inhibits the growth, replication, or spread of viruses. Antivirals are designed to target viral components or processes, with the goal of stopping infection while minimizing damage to the host. They are distinct from antibiotics, which act mainly on bacteria, and from vaccines, which prime the immune system to prevent infection rather than treat it.

Most antivirals work by interfering with steps in the viral life cycle, such as entry into cells, replication of viral genomes, processing of viral proteins, or release of new virions. Common categories include nucleoside and nucleotide analogs that inhibit viral polymerases (for example, acyclovir for herpesviruses, zidovudine for HIV, and remdesivir for several RNA viruses), protease inhibitors that block viral protein processing (used in HIV and hepatitis C regimens), neuraminidase inhibitors that reduce influenza virus release (oseltamivir, zanamivir), and entry or fusion inhibitors (e.g., enfuvirtide for HIV, maraviroc as a CCR5 antagonist). Monoclonal antibodies and interferons also play antiviral roles for certain infections, and newer drugs target RNA polymerases or specialized viral enzymes.

Antivirals are used to treat acute infections, control chronic viral diseases, and, in some cases, prevent infection after exposure. While highly effective for many viruses, antivirals are not curative for all infections and resistance can develop with prolonged use or widespread transmission. Combination therapy, especially in HIV and hepatitis C, helps prevent resistance and improve outcomes. Side effects and drug interactions vary by agent and virus.

Vaccines remain the primary preventive tool against viral diseases, and antiviral development continues to address emerging viruses, resistance, and broad-spectrum activity.