Influenza is a serious illness that can make you miserable. At its worst, it can be fatal.

As North America enters its first full flu season since the start of the COVID-19 pandemic, many are wondering about the intersection of these two respiratory viruses. University of Chicago Medicine Associate Professor Allison Bartlett, MD, MS, is here to answer those questions—including what might happen if we wind up facing a “twindemic,” the collision of the COVID-19 pandemic and a particularly bad seasonal flu.

An infectious diseases expert and associate director of the Infection Control Program at UChicago Medicine, Bartlett has some good news: Many of the steps we take to protect ourselves from the coronavirus are the same things we need to do to remain safe from influenza. In the following Q&A, Bartlett explains what you need to know to stay safe this winter from both influenza and COVID-19.

Q: How will COVID-19 impact North America’s flu season? 

We base our flu season predictions on influenza activity the Southern Hemisphere where the seasons are reversed. Their flu season was more mild than usual, and I remain optimistic we’ll see that here. But most people believe the Southern Hemisphere’s mild influenza season was actually due to all of the safety precautions that were in place because of the coronavirus. Masking, washing hands and staying at least 6 feet away from other people are very effective at preventing the spread of both COVID-19 and the flu. Plus, most children were home from school, which helped minimize flu transmission.

Q: How concerned are healthcare providers about the intersection of a bad flu year and COVID-19?

We’re very concerned about the potential impact of these two viruses. A bad influenza season can have a major impact on our hospitals and hospital bed capacity, and that’s without the impact of the pandemic. Layer in a sharp uptick in patients from the coronavirus, and there could be a severe problem across the country.

Q: Does COVID-19 or influenza pose a greater risk for people this season? 

Either virus can make you very sick or lead to death, but with influenza we have the opportunity to focus on prevention because we have additional tools in our arsenal that help decrease overall infections. There are definitely patient populations that are more at risk for severe complications for each infection. Elderly patients and those with chronic underlying conditions seem to be much more likely to get severely ill with COVID-19. And kids, especially infants under 1, and pregnant women are more likely to have severe infections with influenza.

Q: Can you get COVID-19 and the flu at the same time? What happens if you do?

There’s no biological reason you can’t get COVID-19 and the flu at the same time, and we really don’t have a great answer to what that could look like. Flu alone is going to make you miserable. COVID-19 alone is going to make you miserable. It’s not an unreasonable assumption that the two of them together could make someone very, very sick.

Q: Does having COVID-19 give you any antibodies against a respiratory virus like the flu? 

There are some infections that are less likely to happen after you have the flu. However, we don’t know if COVID-19 is going to be one of those. Unfortunately, there is no antibody level cross protection from flu and COVID-19. Your ability to fight off one is independent of the other. What we don’t understand, on a biological basis, is what happens if you’re exposed to COVID-19 or influenza after your lungs/airways have already been damaged by a recent infection. The science just isn’t out there yet.

Q: How can you tell if you have flu or COVID-19? 

The best way to tell if you have influenza or the coronavirus is to get tested. Symptoms are virtually indistinguishable, with the notable exception that some people with COVID-19 lose their sense of taste and smell. Add in the fact that people can have either infection without symptoms, and it’s basically impossible to tell one from the other on your own. Testing determines the best treatment and whether there needs to be contact tracing. The good news is that many healthcare providers who are doing coronavirus tests should be able to test you for flu at the same time.

Q: Will the flu shot protect me against the coronavirus?

The flu shot will help prevent people from becoming sick from influenza but won’t provide specific protection against COVID-19. However, the fewer people who are sick at once, the better things are on a community level—whether that’s from flu or from the coronavirus. It’s why we’re pushing the flu vaccine so hard this year and pushing people to get it earlier than usual. If there’s a resurgence of COVID-19, it may be hard to access healthcare providers to get flu shots later in the season.

Q: Can Tamiflu or the flu shot treat COVID-19? 

Tamiflu or a flu shot will not directly treat or lessen the symptoms of COVID-19. And, unfortunately, we don’t have vaccine or a readily available treatment for COVID-19 that’s accessible for patients. At this point, all we can do is treat the symptoms of COVID-19. But you can get vaccinated against the flu, which can prevent an infection or lessen its severity. And if you get sick with influenza or have been exposed to it, you can take antiviral medication like oseltamivir (Tamiflu) to prevent getting sick.

Q: What should you do if you develop influenza or COVID-19 symptoms? 

If you have any respiratory symptoms, stay home, stay away from other people and try to isolate yourself to prevent the spread to others. If you have access to testing, try to get tested within 48 hours of the start of your symptoms. If it’s influenza, your healthcare provider can prescribe medication to help your symptoms improve faster. We used to encourage people to wait several days before getting COVID tests, but new research shows tests can be accurate early on. It’s also helpful to get tested for COVID-19 as soon as you can to expedite contact tracing.

Q: Will the pneumonia vaccine protect me against the flu or COVID-19? 

The pneumonia vaccine helps protect against a variety of bacteria that can cause bacterial pneumonia, which can develop several days to a week after a viral infection. The pneumonia vaccine won’t prevent flu or COVID-19, but it can help prevent complications that may come after.

Q: Can I boost my immune systems to protect against flu or COVID-19? 

I wish there were a list of things we could do to help our immune systems to keep us from getting sick with the flu or the coronavirus. But there’s no magic immune-boosting drug. Instead, focus on eating a healthy, varied diet and getting enough sleep. Also, make sure you’ve got any chronic medical conditions under control.

Q: Can I do anything to decrease my chance of getting very sick if I’ve been exposed?

Once an exposure to influenza or COVID-19 has happened, there’s not a lot we can do to modify who gets sick from it. If you’ve got influenza, your physician may give you some medication like Relenza (zanamivir), Tamiflu (oseltamivir) and Rapivab (peramivir). The best thing you can do is focus on prevention.

—A version of this story was first published by University of Chicago Medicine.