An antiviral is a substance that fights against viruses and inhibits their growth. A doctor may prescribe antiviral medications to help treat a viral infection, and people can use antiviral products to prevent the growth and spread of viruses.

Any substance that slows the replication of viruses is an antiviral. Viruses are microscopic organisms that can infect animals, plants, fungi, and bacteria. Researchers suggest that viruses are the most abundant biological entity on the planet. The structure of viruses means that only antivirals can eliminate them — other medications, including antibiotics, are not effective.

Viruses consist of a protein coat, called a capsid, that surrounds core genetic material, which is either DNA or RNA. Viruses are unable to replicate without a host cell. Therefore, to survive, viruses must infect cells and use these cells to make copies of themselves. In the process of doing this, they can kill these cells and cause damage to the host organism, which is why viral infections can make people ill.

This article looks at the difference between antiviral, antimicrobial, antibacterial, and antifungal substances. It also explores the effectiveness of antiviral drugs, masks, cleaning products, and herbs.

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Antimicrobial substances act to destroy or inhibit the growth of microbes. The term microbes refers to microscopic organisms, which include bacteria, fungi, and viruses. People can further divide antimicrobials into antibiotics, antifungals, and antivirals, with the name of each of these referring to the microbe that the substance targets.

For example, antiviral substances fight against viruses and are not effective against bacteria or fungi. Conversely, antibiotics and antifungals will have no effect on viruses. Antivirals work to prevent viral infection, replication, and growth.

Most antivirals target a specific virus, but some broad-spectrum antivirals are available that work against multiple viruses.

Antiviral drugs do not directly destroy the virus but work by preventing the infection process. As viruses need to infect and replicate in host cells to survive, preventing this process allows antiviral medications to combat viruses. An antiviral drug can do this in several ways:

  • Blocking infection: Viruses cannot replicate without a host cell. Some antiviral drugs work by tricking the virus into attaching to them rather than a human cell. Without a human cell, the virus cannot replicate, so it dies.
  • Interrupting replication: Once a virus enters a host cell, it begins to replicate. Some antiviral drugs disrupt the replication process within the cell, reducing the severity of symptoms and possibly speeding recovery.
  • Preventing spread: After replication, the virus particles enter the bloodstream. Some antiviral drugs work by preventing the release of these viral copies into the bloodstream, which reduces the spread of the infection.

Examples of antiviral drugs include oseltamivir (Tamiflu), which tackles influenza, and acyclovir (Zovirax), which treats herpes and chickenpox.

In addition to prescribing antiviral medications, doctors may recommend vaccinations. These differ from antivirals but are another safe and effective way to combat viral infections. Instead of using antiviral agents to prevent the infection process, vaccinations prepare the immune system to detect and eradicate viruses.

Wearing face coverings has been critical in preventing the spread of SARS-CoV-2 and the severity of COVID-19. However, the effectiveness of different types of face coverings can vary greatly. Some may feature an antiviral coating to make them more effective.

A 2021 study highlights that coating masks with a glycoprotein called lactoferrin may help provide further protection and prevent the transmission of viruses. Lactoferrin mimics the sticky carbohydrates present in the throat and nasal passages, which allows it to capture viral particles in airborne droplets and stop them from infecting a person.

Another 2021 study notes that infusing masks with quaternary ammonium salts can also help protect against viral contamination by inactivating viruses. Research highlights the antiviral properties of quaternary ammonium compounds against a broad spectrum of viruses.

Several commercial cleaning products may kill harmful viruses. These products can contain various active ingredients and will usually advertise their effectiveness against viruses. Two active ingredients that household cleaning products commonly include are sodium hypochlorite and hydrogen peroxide.

These two chemicals are oxidizing agents and are capable of inactivating viruses. They do so by destroying the protein coating that protects the viral genetic material. This means that the virus can no longer reproduce. Research suggests that both of these disinfectants are effective in inactivating coronaviruses on household surfaces.

Evidence also indicates that alcohol at concentrations of 60–80% demonstrates antiviral properties. A 2020 study reported that alcohol-based hand rub solutions could inactive SARS-CoV-2, which causes COVID-19.

Several common herbs may also have antiviral properties. Their concentrated plant compounds may act to kill viruses or reduce the symptoms of the resulting diseases.

For example, oregano contains a key plant compound called carvacrol, which possesses antiviral properties that evidence suggests might be effective against SARS-CoV-2.

A 2017 study notes that compounds present in peppermint leaf extract exhibit antiviral activity against the respiratory syncytial virus. Another 2017 study indicates that sage contains compounds that possess antiviral properties.

Rosemary may also have antiviral effects. A 2018 study highlights that a compound present in rosemary called oleanolic acid displays an antiviral response against HIV and influenza. Rosemary essential oil also shows antiviral activity against hepatitis A.

Antiviral substances work to inhibit viral activity by preventing the virus from developing, replicating, and spreading. They fit under the antimicrobial umbrella but differ from antibacterial and antifungal products.

Antiviral substances include antiviral medications, which a doctor may prescribe to treat a viral infection. They also include masks and cleaning products, which may help prevent the spread of viruses, and some herbs, which have antiviral properties.