Do antibiotics work for viruses?

The change in temperature as winter settles in often leads to increased respiratory symptoms such as sneezing, congestion and coughing. But how do you know if your symptoms are due to a virus or bacteria?

In this Q&A, pediatric infectious disease specialist Paul Krogstad, MD, sheds light on viral versus bacterial illnesses. And he talks about when you should use antibiotics for infections.

Q. What is the difference between a viral infection and a bacterial infection?

A: Bacteria are single-celled organisms that grow and divide by themselves. As long as they have a source of nutrients, they can grow and spread.

Viruses are the simplest life form, so simple that some would argue they aren’t life forms at all. They can’t grow on their own. Instead, they are parasites that must invade cells in order to replicate.

Q. Do antibiotics work on viruses and bacteria?

A: Antibiotics only work for bacterial infections. They work by destroying the bacteria or keeping them from growing out of control. The right antibiotic will do this with little to no harm to the body.

Q. How do antiviral drugs differ from antibiotics?

A: Antiviral medications don’t destroy the virus. They work to prevent the virus from replicating to the point where it causes problems. By slowing the replication, the body’s immune system can keep the virus in check.

Q. Will a virus ever turn into a bacterial infection?

A. Sometimes, viruses will damage tissues like the lining of your nose or lungs. The bacteria take advantage of the damage caused by a virus to get past the body’s normal defenses and grow out of control.

Q. How do we know if an infection is viral or bacterial?

A. There isn’t an easy way to separate the two perfectly. Instead, physicians look at patterns and symptoms to discern whether an infection is viral or bacterial. For example, having a runny nose with clear discharge for a week is likely viral. If it continues longer and you develop facial pain or a yellow-green discharge, it may be that a bacterial infection has taken root.

People need to be very specific about their symptoms and how long they’ve had them when contacting their doctor.

Q. When is it appropriate to use an antibiotic?

A. Physicians know there are many examples where they should prescribe antibiotics right away. But the more we learn, the more we realize there are some cases where they aren’t immediately necessary. For example, this is true with ear infections in children over age 2.

Q. Are there downsides to taking antibiotics?

A. Most antibiotics are entirely safe, though there are possible side effects and sometimes a person’s response to an antibiotic is unpredictable. We’ve also learned that there are good bacteria in the body that help keep us healthy, that we don’t want to kill with antibiotics. Doctors try to strike a balance between destroying the harmful bacteria and keeping the healthy ones.

The other concern is antibiotic resistance. When we overuse antibiotics, the bacteria could adapt to them. So, you’ll need a higher dose or a more potent antibiotic, which comes with a greater risk of side effects or harm.

Q. Are antibiotics effective for COVID-19?

A. If you’re hospitalized with COVID-19, there is a high likelihood your provider won’t prescribe antibiotics since a virus is the cause of your illness. Physicians operate under the cardinal rule of “first, do no harm.” We want to deliver treatment that helps you recover without causing other potential concerns. Antibiotics could be unsafe for people with COVID-19 because they alter how the body handles other vital medications. We are judicious in thinking about you holistically — your kidneys and heart — so we don’t offer medicine that could potentially do more significant harm.

If you are experiencing symptoms such as cough, runny nose, congestion or fever, you can reach out to your primary care provider. He or she will determine if you should seek testing or treatment.


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