A triple threat of overlapping illnesses -- COVID-19, respiratory syncytial virus (RSV) and influenza -- is overwhelming healthcare systems and leaving Americans sick this holiday season.

Medical experts say the so-called "tridemic" is partially fueled by the early flu season, while COVID variants continue circulating. Respiratory syncytial virus, or RSV, is a common cold-like illness that peaks in late December, but due to the relaxing of COVID safety protocols like masking and social distancing, the virus is surging.

Dr. Bruce Farber is the Chief of Public Health and Epidemiology at Northwell Health, while Dr. Thomas Bader is the Chief Clinical Officer at Hackensack Meridian Health. Here's what both medical experts want you to know about this season's spread.

What Are the Symptoms?

Unfortunately, from a sole symptoms perspective, the three illnesses overlap, but there are hints that could give off clues. Testing is the best way to define exactly what virus one may have contracted.

"For example, if you have lost your taste or smell, you can almost be certain that the virus is COVID because the other viruses don't do that," said Dr. Farber in a recent interview with NBC New York.

A sudden onset of symptoms paired with a high fever could link more with the flu. RSV is similar to a bad cold with a fever happening more so in children rather than in adults. Those under the age of six months may develop bronchitis, bronchiolitis or difficulty breathing.

Who is Most at Risk?

There are four groups of people that should be concerned when contracting either COVID, flu or RSV - younger children, elderly, immunocompromised and pregnant women.

"Pregnant women who get viral infections do much worse compared to their nonpregnant peers. A young, healthy woman in her 30s is more likely to get through any of these viral illnesses without too much of a challenge. You add pregnancy, and the risks of complications are much greater," Dr. Bader told News 4, who continued to stress early vaccinations and contact with a health care provider for those women.

When to Visit the Emergency Room?

According to Dr. Bader, patients should have a relatively low threshold when considering a visit to the ER as these viral infections have therapies that can be taken at home. However, symptoms that warrant immediate attention are difficulty breathing, speaking full sentences or experiencing high fever.

It is recommended to contact your health care provider before reaching a level of seeking admission into the emergency room.

Why the Sudden Uptick in Cases?

While no one can be exactly sure as to why the tridemic cases are mounting, experts believe it is due to a few factors. As facial covering and physical distancing precautions have slowed down, the public is more prone to viral infections, especially during the holiday season with social gatherings and office parties.

Vaccination rates for influenza are below what they had been prior to COVID.

"For adults, they [flu vaccination rates] are 26%, and for children, they are in the low 40s. We're often much higher than that. I think people are vaccine shy for all vaccines, and that's unfortunate in my opinion, but if you take that flu vaccine, you're much less likely to be in the hospital for the flu, you're much less likely to die from the flu," shared Dr. Farber.

What Precautions Should You Take?

Fundamental protective measures still apply, such as keeping up vaccinations, frequent hand washing, covering a sneeze or cough, and staying home if there is an onset of symptoms.

It is not too late to get a flu shot. If elderly, Dr. Farber suggests requesting a high titer flu shot with over four times the amount of antigen compared to the regular dose.

What about COVID Reinfections?

While it may be too soon to tell, Dr. Bader says he is concerned about multiple infections and levels of exposure to the coronavirus in regard to possibly developing long COVID, a post-COVID condition where lingering symptoms occur months after the recovery from the initial infection.

"Certainly for someone who has a normal, healthy immune system, the good news is that we have amnesia or what's called anamnestic immunity, so you will have a response to repeat infections. Another hope would be that in subsequent infections, your body would be able to respond so quickly to the infections. Perhaps, that will decrease the inflammatory elements of the infection, and perhaps, those inflammatory elements are the pieces that contribute to long COVID," said Dr. Bader.

To Dr. Farber, emerging COVID variants are inevitable for the foreseeable future until vaccines can target common sites on the coronavirus that do not mutate.