Got the sniffles? Summer colds are rushing back. Here's how to tell if it's COVID-19.

You wake up feeling like you’ve been hit by a truck.

You barely have the energy to get out of bed, your head is heavier than a bowling ball, and your throat feels as if you’ve swallowed a cactus.

But you’re fully vaccinated against the coronavirus. This can’t be COVID-19, can it?

Although breakthrough infections are possible, they’re extremely rare, and health experts say fully vaccinated Americans are more likely to suffer from a severe summer cold than COVID-19.

“We’ve seen a very unseasonal rebound of these infections,” said Dr. Andrew Preston, professor of microbial pathogenicity at the University of Bath in the U.K. “It appears all the isolation that people have gone through has interfered with the seasonality of these infections.”

The easing of social distancing and masking at gatherings may have sparked a rise in cold cases usually seen during the fall and winter months, health experts say. People also may be reporting more cases than before the pandemic because they’re more aware of their symptoms.

Although hospitals and public health agencies don’t officially track cases of the common cold, they do track other infections that could be a marker for colds.

“One of that is RSV,” said Dr. Melanie Swift, an occupational medicine physician who helps lead the COVID-19 vaccination plan at the Mayo Clinic.

Respiratory syncytial virus, or RSV, is a common virus that usually causes mild, cold-like symptoms primarily in children, according to the Centers for Disease Control and Prevention. It’s the most common cause of pneumonia in children younger than 1 in the U.S.

“The big story there is that we’re seeing lots of cases of RSV. ... We never see it in June, July or August. We just don’t,” Swift said.

Swift said doctors are now testing for the coronavirus in many RSV cases "because the symptoms can be indistinguishable.”

Many cold and COVID-19 symptoms overlap: fever, runny nose, sore throat, coughing, and general fatigue. Experts say the only symptom that may distinguish a nasty cold from COVID-19 is the loss of taste or smell.

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There’s also not much difference in illness duration. Symptoms from a cold virus may last seven to 10 days. Experts say COVID-19 symptoms typically appear two to 14 days after exposure and usually last up to two weeks, but it varies by person.

The only "real definitive way" to know the difference between a summer cold or a mild breakthrough infection of COVID-19 is by PCR testing, Preston said.

Regardless of the diagnosis, experts urge Americans who are feeling unwell to stay home and follow public health strategies practiced throughout the pandemic such as masking and good hand hygiene.

“Stay home and take care of yourself and reduce the exposure,” said Dr. Len Horovitz, a pulmonary specialist and internist at Lenox Hill Hospital in New York City. “People don’t want to be around somebody who’s sick.”

Follow Adrianna Rodriguez on Twitter: @AdriannaUSAT.

Health and patient safety coverage at USA TODAY is made possible in part by a grant from the Masimo Foundation for Ethics, Innovation and Competition in Healthcare. The Masimo Foundation does not provide editorial input.

This article originally appeared on USA TODAY: COVID or common cold? Here's the difference, doctors say