(WPRI) — As many get together with friends and family over the holidays, doctors say it’s “highly likely” that respiratory viruses could spread.

Three illnesses — COVID-19, respiratory syncytial virus (RSV) and the flu — have been infesting hundreds of thousands of Americans daily, which can make it hard to tell what’s wrong when you start to experience symptoms.

All three have overlapping symptoms, but a chart, created by Children’s National Hospital in Washington, D.C., compares the most common.

When it comes to the onset of symptoms, the Centers for Disease Control and Prevention (CDC) says COVID and RSV both start gradually before they escalate, whereas the flu usually hits hard and fast.

With RSV, symptoms usually go away in about a week, according to the CDC, but symptoms persist longer with the flu and COVID.

The only true way to know which virus you may have is to take a test.

Although at-home COVID tests are available, PCR tests are still more accurate. The CDC says healthcare providers can also test for multiple viruses at once.

If you test positive for COVID, the CDC says there are precautions you can take to prevent spreading it to others: isolation, masking, and avoiding contact with people who are at high risk of getting very sick

The CDC says regardless of vaccination status, you should isolate yourself from others when you test positive.

If you have symptoms of the flu or RSV, there are laboratory tests that can be done by your doctor.

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