Why are so many people sick right now?

(NEXSTAR) – One week after the Thanksgiving holiday, and chances are good that you are sniffling, coughing or feeling a little scratch in your throat. It's not just you – the country is contending with a "tripledemic" of viruses (not to mention, a whole lot of common cold).

As of late November, reported COVID-19 cases in the U.S. were stable, but high. The Centers for Disease Control and Prevention recorded about 300,000 new cases over the past week, but that number is likely an undercount, as home tests often aren't reported to public health agencies.

Meanwhile, influenza is rising rapidly and on its way to a peak much earlier than the typical flu season. The CDC's preliminary count is rough, but the agency believes as many as 14 million have been sickened and up to 8,400 people have died.

RSV, for example, is a common virus we're exposed to regularly. It's usually hardest on young children and babies, who haven't built up immunity from repeated exposures. This year, adults are getting it a lot, too.

"People have not been exposed to RSV as much, so their bodies have likely stopped making the antibodies," Dr. Jim Scott, Dean of Touro University California College of Pharmacy, told Nexstar's KRON. It's not that our immune systems forgot how to create the necessary antibodies, but it just takes some time for antibody production to "ramp up and meet the need."

Staying home, masking and avoiding large gatherings wasn't just effective at curbing the spread of COVID – it also brought the levels of flu transmission and other respiratory viruses way down. Pretty much all of those measures have been lifted, and viruses have started spreading rapidly again.

"It's a normal process that we see here. It's just that without seeing it for three years, we now have this large bounce back to bring us back to equilibrium," Pekosz said.