Americans face an uncertain and anxiety-filled holiday season for the second consecutive year, as the highly contagious omicron variant threatens to intensify an already alarming surge of COVID-19 cases.

Public health officials have voiced deepening concerns about the rising number of infections — still fighting the effects of the delta variant — could find themselves stretched beyond their limits if the two variants combine to create a fresh wave.

Maine set a record for the number of hospitalized COVID patients on Wednesday, a day after Michigan hit a new high. New Jersey recorded its highest number of cases on Thursday since mid-January, at the peak of last winter's surge.

Over the past month, new cases have risen nearly 40% to a 7-day average of 121,000 new infections per day, according to a Reuters tally. That represents more than half of the level at this point in 2020, days after the first coronavirus vaccine was approved for emergency use.

Deaths have risen 18% since mid-November to an average of 1,300 lives lost a day. COVID hospitalizations have risen about 45% over the last month.

Dr. Anthony Fauci, the top US infectious disease expert, said on Thursday that the omicron variant would soon dominate infections.

"We've seen that in South Africa, we're seeing it in the UK, and I'm absolutely certain that's what we're going to be seeing here relatively soon," said Fauci, who will meet with President Joe Biden Thursday afternoon to discuss the government's response.

In South Africa, the United Kingdom and Denmark, the number of new Omicron infections has been doubling every 2 days.

Britain recorded nearly 80,000 new cases on Wednesday, its highest single-day total since the pandemic began, and officials there have warned that hospital admissions could soon hit record levels because of omicron's transmissibility.

Preliminary data suggests omicron may be more contagious than delta but less likely to cause severe illness, though much remains unknown. Research also indicates that the two-dose vaccine regimens have vastly reduced protection against omicron but that a third booster dose restores much of the vaccine's efficacy.

In New York City, the percentage of people testing positive for COVID-19 doubled in 3 days, according to Dr. Jay Varma, a senior public health adviser to Mayor Bill de Blasio.

"Um, we've never seen this before in #NYC," he wrote on Twitter, adding that the only explanation is omicron's ability to evade both natural and vaccine-induced immunity.

The surge has prompted worried Americans to reconsider holiday travel plans for the second consecutive year. Experts have said vaccinated individuals can travel safely as long as they wear masks and avoid unnecessary risks such as large crowds and indoor gatherings.

After months of planning a trip to Florida to see his parents for Christmas and his mother's birthday, Kalaya'an Mendoza of Queens, New York, told Reuters he was forced to cancel it when he learned that several people at an event he attended on Monday had tested positive.

"I'm a little bit wrecked," Mendoza, 43, said in an interview on Thursday. "It feels like 2020 all over again. I had to weigh my very intense Filipino need to be with family with their care and safety."

Mendoza, who has not seen his parents since December 2019, said he was angry at how little progress the US government had made on fighting the pandemic while spending billions of dollars this year on other items, such as the military.

"I remember watching my neighbors get carted away in body bags at the start of this pandemic, and two years in, we shouldn't be here," he said.

The increasing caseload has wreaked havoc on efforts by companies to return to normalcy, including postponing plans to bring workers back to the office. Citigroup Inc has told New York-based employees that they can work from home through the holidays, people with knowledge of the matter told Reuters on Thursday.

The United States leads the world in daily infections, accounting for 1 in every 5 cases reported globally. The country has seen more than 800,000 deaths and 50 million infections since the pandemic began.

At least 36 states have reported confirmed omicron cases, CDC officials said on Wednesday.

The National Hockey League and the National Basketball Association have canceled several games this week after COVID-19 outbreaks hit several teams.

The National Football League has not yet announced any postponements after nearly 100 players were placed on the COVID-19 reserve list, including more than a dozen Cleveland Browns, who are scheduled to play the Las Vegas Raiders on Saturday.

(Reporting by Julia Harte and Joseph Ax in New York; Additional reporting by Barbara Goldberg, Tyler Clifford and Matt Scuffham in New York; Brendan O'Brien in Chicago; and Noor Zainab Hussain in Bengaluru; Editing by Lisa Shumaker)