Between a surge of COVID-19 variants, an active flu season and other spreading viruses, determining what an illness is can be tricky. 

Experts say that testing is the best way to find out for certain because overlapping symptoms could cause confusion. 

NEW YORK, FLORIDA SHATTER SINGLE-DAY RECORDS FOR COVID-19 CASES

For example, influenza symptoms include a fever or chills, cough, sore throat, runny or stuffy nose, muscle or body aches, headaches, fatigue and some vomiting and diarrhea. 

Symptoms of COVID-19 include fever or chills, cough, fatigue, shortness of breath muscle or body aches, headache, sore throat, congestion or runny nose, new loss of taste or smell, nausea or vomiting and diarrhea. 

Common colds tend to be milder, with symptoms including a stuffy nose and sore throat. 

A girl blows her nose (Credit: iStock)

Viruses that cause colds, flu and COVID-19 are spread through droplets from the noses and mouths of those infected – even before symptoms occur.

The time for when someone starts to feel sick varies and some people infected with the coronavirus are asymptomatic, while still having the ability to spread the disease.

Recently, reports have spread about a co-infection nicknamed "flurona," when a person catches COVID-19 and the flu at the same time.

CDC: FLU VIRUS DETECTIONS ON THE RISE, EARLY SIGNS VACCINATION DOWN

However, the viruses have not merged to create a new illness.

In order for medical professionals to prescribe the right treatment for their patients, testing plays an important role. 

While at-home tests for flu aren't as widely available as rapid tests for COVID-19, some pharmacies offer testing for both.

Getting vaccinated helps reduce the spread of the viruses.

The Centers for Disease Control and Prevention (CDC) says everyone 6 months and older should get a flu vaccine every season – especially those who are at higher risk. 

Children ages 5 years and older and adults who are eligible are instructed to get vaccinated against COVID-19 regardless of whether they already have been infected. 

CLICK HERE TO GET THE FOX NEWS APP

"Evidence is emerging that people get better protection by being fully vaccinated compared with previously having a COVID-19 infection," according to the agency.

The CDC says it is safe to get a flu and COVID-19 shot or booster at the same time.

The Associated Press contributed to this report.