What Is Antiviral Resistance?

Close up of flu virus
What does it mean when antiviral medicine doesn't work?. Ian Cuming / Getty Images

You may have heard of antibiotic resistance - when bacteria have changed so that antibiotics no longer kill them or stop their growth. It's a growing problem that could impact our lives in signifcant ways in the future. But there is another type of drug resistance that could affect us as well. Antiviral resistance is a term used to describe viruses that have developed resistance to antiviral medications.

It is most commonly used in relation to the flu and medicines that are used to treat it. 

Antiviral medications such as Tamiflu (oseltamivir) and Relenza (zanamivir) are commonly prescribed to treat influenza. Although they don't cure or kill the virus, they can shorten the duration of the flu and make your symptoms less severe. There is also an IV antiviral medication called Rapivab (peramivir) that is used to treat the flu in patients that are hospitalized. 

There are two other antiviral drugs that are not used in the United States because all of the circulating influenza viruses are resistant to them, which means they don't work. They are classified as adamantanes (amantadine and rimantadine). Nearly all flu viruses that cause illness in humans are resistant to these medications. 

There are some strains of the flu that have developed resistance to oseltamivir as well. In a given flu season, there are typically a small number of people that are infected with a strain of the flu that is oseltamivir resistant.

When this happens, taking Tamiflu won't help. 

How Do We Know Flu Viruses Are Drug Resistant?

The US Centers for Disease Control and Prevention (CDC) monitors influenza viruses throughout flu season. They track which strains of the virus are causing illness in people and also perform tests to see if they are resistant to the antiviral drugs that we use.

In recent years only a small number of flu viruses tested have been resistant to Tamiflu. 

If a drug resistant strain of the influenza virus were to become dominant, the CDC and Advisory Committee on Immunization Practices (ACIP) would change their recommendations for flu treatments. 

What Can You Do?

The best thing you can do to protect yourself from the flu is to get a flu vaccine every year. If you choose not to get one, it's probably because you believe one of these common myths about the flu vaccine. Get the facts and then get your vaccine. If you think you just don't need one because you are usually healthy, being healthy won't protect you from the flu. Even if you have never had it before, you could get it at any time and it will make you feel terrible and interrupt your life for at least a week. A simple vaccine could prevent that. 

If you can't get the vaccine, do what you can to keep yourself healthy. Wash your hands and avoid people that are sick as much as possible. 

Researchers are constantly working to develop better flu vaccines and treatments.

Until then, we all need to do our part to prevent it.

Sources:

"Influenza Antiviral Drug Resistance". Seasonal Influenza (Flu) 16 Sep 15. US Centers for Disease Control and Prevention. Department of Health and Human Services. National Institutes of Health. 30 Jan 16. 

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