"The virus transmission that took place during the Thanksgiving period has brought many health systems across this country to the brink of failure and we are still not yet finished seeing that impact," said Dr. John Brownstein, chief innovation officer at Boston Children's Hospital and an ABC News contributor.
In the weeks following Thanksgiving, national and state COVID-19 numbers have hit records, and December has become the worst month in terms of COVID-19 cases in the U.S, with over 4.5 million confirmed cases, according to data collected by The COVID Tracking Project.
Since late November, the national seven-day average of new cases has increased by 32%, with 12 days this month recording a daily case load over 200,000.
Hospital beds numbers across the country are also dwindling, with deaths surging to unprecedented levels on a daily basis.
There are currently more than 117,000 patients hospitalized nationwide, a record high, and just in the last three weeks, over 54,000 COVID-19 related deaths have been recorded, putting December well on track to become the deadliest month on record.
"Layering in the December holiday travel and gatherings means we will have a third jump in this wave, or a surge on surge on surge," Brownstein added. "Unfortunately, this increase will likely lead to catastrophic impacts on hospital capacity and the acceleration of terrible mortality milestones through February."
Dr. Anthony Fauci, the nation's top infectious disease expert, said in a conversation with the JAMA Network earlier this month that he too is "really concerned" about the prospect of the virus in the coming months.
"We are going to have more people traveling and instead of just having a weekend of the holiday, it's well over a week. It's Christmas and the week between Christmas and New Year's [Eve] and then New Year's [Day]," Fauci said.
Moncef Slaoui, head of Operation Warp Speed, echoed Fauci's warnings, predicting higher numbers of infections and daily deaths with the upcoming Christmas gatherings, which would further compound the surge due to Thanksgiving.
"It will get worse, because we are still experiencing the outcome of the Thanksgiving holidays, and the gatherings, and unfortunately there may be more over the Christmas holiday ... so there will be a continuing surge," Slaoui said during an appearance on CNN on Sunday.
In preparation for the potential fallout, the Centers for Disease Control and Prevention released new guidance last week that strongly recommended postponing travel and staying home this year as "the best way to protect yourself and others."
But despite the warnings, millions are still traveling this holiday season. The Transportation Security Administration reported Tuesday it has already screened more than 4 million travelers in the last four days.
"The sheer volume of mobility we are witnessing is well beyond what we saw over the Thanksgiving period. Travel plus the duration of this holiday period means that we will likely see more significant virus spread than any of the other holidays during the pandemic," Brownstein said.
Furthermore, there are growing concerns about the potential implications in the U.S. of the new variant of the coronavirus identified in the United Kingdom, which European health officials say may be 70% more transmissible than the old variant.
Fauci told ABC News' "Good Morning America" on Tuesday that it is "certainly possible" that the U.K. variant is already in the U.S., which experts say may result in an even greater post-holiday surge in cases.
"If the new more transmissible U.K. variant is already circulating, we may see an even steeper acceleration of cases and hospitalizations," Brownstein said.
While prepared, the CDC said it has yet to detect the new variant in the United States. It is not uncommon for viruses to mutate, officials caution.
Ultimately, Fauci told ABC News, officials do not "want to cancel Christmas," but it is critical that Americans follow the guidelines set by health officials, explaining that people must "tone down plans, try to minimize travel and try to avoid large congregations of people indoors."
"There is light at the end of the tunnel. Within the next several months, vaccines are going to make a serious, important, positive impact," Fauci said. "But until then, we really need to adhere to good, prudent public health practices."