Omicron updates: COVID-19 cases could double in New York City

New York City Mayor Bill de Blasio on Monday announced a vaccine mandate for all private sector employees.

On the talk show "Morning Joe," the mayor called the mandate, which goes into effective Dec. 27, a "preemptive strike."

New York City will also now mandate two vaccine doses, instead of one, for indoor activities, and will require proof of vaccination for indoor dining for kids ages 5 to 11.

Peter McGinn was one of the first known people in the United States to contract the omicron variant.

The 30-year-old Minnesota resident, who is fully vaccinated against COVID-19 and has received a booster shot, said he believes he became infected after attending a massive anime convention in New York City in late November. McGinn said he and several other attendees, who are also fully vaccinated, went out together after the event. Half of that group has since tested positive for COVID-19, according to McGinn.

McGinn said he tested positive after returning home to Minnesota and learning that a friend with whom he attended the convention had contracted the virus.

"I felt perfectly safe with the people that I was with, and so it never really crossed my mind to think that I had COVID," McGinn told ABC News on Sunday. "I was just a little taken aback."

Several dozen cases of omicron, a newly discovered variant of the novel coronavirus, have now been reported in at least 17 states across the country, according to Dr. Rochelle Walensky, director for the Centers for Disease Control and Prevention.

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Health officials on alert as omicron variant spreads

The emerging variant has now been reported in at least 17 U.S. states, as demand for COVID-19 vaccine shots rises and officials stress the importance of getting boosters.

ABCNews.com

At least 17 people aboard a Norwegian Cruise Lines ship docked in New Orleans have tested positive for COVID-19, officials said Sunday.

The cases were found among both passengers and crew members on the Norwegian Breakaway cruise ship. A probable case of the omicron variant was also identified among a member of the crew, who is not a Louisiana resident and did not leave the ship, according to the Louisiana Department of Health.

Earlier Sunday, Louisiana confirmed its first case of omicron, which the health department said did not include any of the passengers or crew members from the Norwegian Breakaway.

The Norwegian Breakaway had departed New Orleans on Nov. 28 and returned this weekend as scheduled. Over the past week, the cruise ship made stops in Belize, Honduras and Mexico.

The ship docked in New Orleans on Sunday and all individuals on board were tested prior to disembarkation, according to a spokesperson for Norwegian Cruise Lines.

"In addition to requiring that 100% of guests and crew are fully vaccinated, per the Company’s comprehensive health and safety protocols, we have implemented quarantine, isolation and contact tracing procedures for identified cases," the spokesperson told ABC News in a statement Sunday. "Any guests who have tested positive for COVID-19 will travel by personal vehicle to their personal residence or self-isolate in accommodations provided by the Company according to CDC guidelines."

All of the identified cases on board were asymptomatic, according to the spokesperson.

"We take this matter extremely seriously and will continue to work closely with the CDC, the office of Governor John Bel Edwards, the Louisiana Department of Health as well as the city and port of New Orleans," the spokesperson added.

-ABC News' Mina Kaji and Anthony Mcmahon