The New York City Fire Department announced Sunday that 61-year-old Joseph Ferrugia is its first active firefighter to have died of COVID-19.

He is the 13th member of the FDNY to die of coronavirus.

“This horrific illness has taken far too many lives, and now it has killed a man who bravely served New Yorkers for three decades," Fire Commissioner Daniel A. Nigro said in a statement Sunday. "He ran toward danger his entire career, searching for those trapped by flames and doing all he could to save them. Our entire Department mourns his loss.”

Ferrugia joined FDNY in 1990 and was a World Trade Center first responder, the department said.

FDNY said he is survived by his three adult children and three siblings.

Chicago Public Schools pushed back the return of in-person classes for kindergarten through eighth-grade students by one day as negotiations continue between the city and the Chicago Teachers Union.

While the district and union leadership agree on some items of contention in principle, Mayor Lori Lightfoot said at a press conference Sunday that the union has refused to put those agreements in writing and instead has added more items to the negotiating table that are not related to the public safety issues associated to reopening some classrooms during the COVID-19 pandemic.

Just minutes before Lightfoot was expected to appear in a presser Sunday, CTU sent a series of tweets that hinted there was not going to be a deal just yet.

The mayor said she still expects CPS teachers to show up to their classrooms despite the dispute. Last week she said that if they do not, she would be forced to take further action, but did not specify what that action would be.

The U.S. Centers for Disease Control and Prevention released its latest update Sunday on the country's coronavirus vaccine rollout.

There have been close to 50 million doses distributed around the country, according to the agency's online tracker. Of those doses, 31 million, roughly 62%, have been administered, according to the CDC.

About 25 million people have received their first dose and 5.6 million have received two doses, the CDC said.

A city on Florida’s panhandle put on its Mardi Gras parade as planned, despite its high positivity rate.

Prior to the parade on Saturday, Milton Mayor Heather Lindsay advised residents to take their temperature before attending the event and for everyone who attends the party after the parade and participates in the kid’s zone to wear a mask.

"I would love to focus only on the fun and pageantry of it all because I love Mardi Gras, but we must accept life on life's terms," Lindsay wrote. "Presently we are in the midst of a widespread outbreak of a virus that is not just the flu."

The city currently has a positivity rate of 18%, "well above" the state average of 6.62%, Lindsay wrote. Households affected in Milton reduced from a high of 102 to 90 this week, but the local positivity rate has been as high as 28% and "never lower" than 16%, she added. The population in Milton is about 10,000.

It is unclear how many people attended the event.

American biotechnology company Regeneron Pharmaceuticals announced Wednesday that its cocktail of two monoclonal antibodies held up in laboratory experiments against new variants of the novel coronavirus first identified in the United Kingdom and South Africa.

Monoclonal antibodies are synthetic versions of our natural antibody defense to infection. They are being studied as a way to both treat and prevent COVID-19 infection, with promising results. But unlike vaccines, which are thought to offer broader protection, some scientists have been worried that this type of therapy would be less effective against newly emerging variants of the virus.

Wednesday's announcement is good news for Regeneron's monoclonal antibody treatment, REGEN-COV, though the data is still preliminary and currently under peer review.

Regeneron scientists as well as researchers at Columbia University in New York City have each independently confirmed that the casirivimab and imdevimab antibody cocktail successfully neutralized both the U.K. and South Africa variants when tested against them, according to a company press release.

REGEN-COV has not yet been tested against another variant that was first identified in Brazil. However, Regeneron said the two-antibody cocktail "is expected to remain similarly potent" based on some resemblance which the Brazil variant bears to the South Africa strain. The company said it is pursuing further confirmatory research.

It's the latest piece of promising news about the efficacy of monoclonal antibodies as treatment for COVID-19. On Tuesday, American pharmaceutical firm Eli Lilly and Company announced that a combination of two monoclonal antibodies, bamlanivimab and etesevimab, was found to be effective in COVID-19 patients at high risk of severe infection, reducing the risk of hospitalization and death by 70%, according to the results of a final-stage trial.

That same day, Regeneron announced its antibody cocktail had shown positive initial results in prophylactic use -- that is, helping ward off COVID-19 in those who may have been exposed to the virus. Regeneron’s chief scientific officer, Dr. George Yancopoulos, said he hopes the drug "may be able to help break this chain" of active infection and transmission.

Last Thursday, Eli Lilly released data showing bamlanivimab may help prevent disease and stop outbreaks among residents and staff of long-term care facilities.

ABC News' Sasha Pezenik contributed to this report.