The new omicron variant makes up nearly 100% of the strains found in wastewater samples in Orlando, Florida, officials said Thursday.

"It escalated rapidly," Orange County Utilities spokeswoman Sarah Lux told ABC News.

In its first test for the variant last Thursday, the department found no evidence of omicron in the community's wastewater, she said. On Saturday, it represented about 30% of the strains found in the samples, and by Tuesday, nearly 100%.

"So, we're talking about zero to nearly 100 in a matter of a week," Lux said.

All parts of the county are seeing an increasing presence of the omicron variant, she said. The southern area, home to the theme parks, has seen the highest amount of virus remnants, followed by the eastern area, which is home to the University of Central Florida.

-ABC News' Arielle Mitropoulos

The CDC's advisory committee recommended Thursday that people who have a choice should get an mRNA vaccine, either Pfizer or Moderna, over the single-shot Johnson & Johnson vaccine after a review of new CDC data on rare blood clots linked to J&J.

The vote was unanimous.

The rare blood clots are not a new safety concern and the vaccine has already become far less common in the U.S. after it was given an FDA warning label about the clotting condition. But more data that confirmed a slightly higher rate of clotting cases and deaths than was previously reported caused the CDC and FDA to take another look at the data this week.

The CDC has confirmed nine deaths and 54 cases from the severe clotting event, thrombosis with thrombocytopenia.

There could also be more cases and deaths because TSS is under-diagnosed and could be underreported, the CDC said.

The clotting is more common among women in their 30s and 40s but has been seen in adult men and women of all ages.

The experts said J&J should not be taken off the shelves and is still far more beneficial than not getting any vaccine at all.

-ABC News' Cheyenne Haslett

Maine and New Hampshire are now averaging more new cases than at any other point in the pandemic, while daily cases in Massachusetts, Vermont, Connecticut, Pennsylvania and Rhode Island are nearing peak levels, according to federal data.

Five of those states -- Connecticut, Maine, Massachusetts, Rhode Island and Vermont -- have the highest full vaccination rates in the country.

In Florida, which has been largely spared from the latest COVID-19 wave, daily cases have increased by 92% over the last two weeks, according to federal data.

-ABC News' Arielle Mitropoulos

COVID-19 cases in New York City have tripled in the last month, officials warned Thursday.

Mayor Bill de Blasio announced a six-point plan to fight the surge, including increasing testing capacity, doubling down on business inspections and distributing 1 million KN95 masks and 500,000 rapid home tests.

"We need to stop this variant," the mayor said. "This variant moves fast. We need to move a lot faster."

-ABC News' Aaron Katersky

The omicron variant could spread two to three times faster than delta, according to a new report from the Imperial College London COVID-19 response team.

The study, which has not yet been peer-reviewed, also estimated that the risk of being reinfected with omicron is more than five times higher than that of delta.

Data could change as more information on omicron's spread is gathered, though the study offers an early indication of how much more transmissible the new variant is compared to delta.

-ABC News' Cheyenne Haslett, Dr. John Brownstein and Sony Salzman