Is it flu, COVID-19, allergies, or a cold?

Jan. 4, 2022

Could your sniffles be caused by COVID-19? Or the flu? A cold? Or maybe allergies? Determining the cause of an illness can be tricky because many share some symptoms such as sniffling, coughing, and feeling tired. But there are important differences according to the National Institutes of Health.

“Distinguishing COVID from flu can be difficult because the symptoms overlap so much,” explains Dr. Brooke Bozick, an NIH expert on respiratory diseases that affect the lungs.

Flu and COVID-19 are caused by different viruses that can be spread among people. Flu is caused by the influenza virus. COVID-19 is caused by SARS-CoV-2. Both can give you a fever, cough, headaches, and body aches.

“Both influenza and COVID can be spread to other people before individuals develop symptoms,” notes Dr. Aubree Gordon, an infectious disease expert at the University of Michigan.

COVID-19 symptoms can take longer than flu symptoms to develop, she explains. Someone with flu usually has symptoms 1 to 4 days after being infected. A person with COVID-19 typically shows symptoms about 5 days after infection, although this can range from 2 to 14 days.

Symptoms of a cold tend to be mild. You may have a runny nose, cough, congestion, and sore throat. But you won’t usually have the aches and fever that are common with COVID-19 and flu. Often, you’ll feel better in a couple of days.

Allergies can cause a runny nose and sneezing. But they’re not contagious. If your eyes, nose, or ears itch, that also could be an allergy.

Allergy symptoms tend to stop when you’re no longer exposed to the cause. Unless you have asthma, allergies typically do not cause breathing problems. Allergies can be treated with drugs like antihistamines, decongestants, and nasal steroids.

Experts are concerned that flu and COVID-19 cases may increase and overlap in the winter. Flu cases usually start to increase around October and peak between December and February. Being infected with flu and SARS-CoV-2 at the same time is possible, as is showing symptoms of both.

NIH release

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