By Nathan Layne and Maria Caspani

(Reuters) – New York has suffered its deadliest day in the novel coronavirus pandemic, with 731 fatalities in the last 24 hours, although Governor Andrew Cuomo said hospitalizations were reaching a plateau in a promising sign for the hardest-hit state.

Even as the total number of deaths reached 5,489 across New York, Cuomo told a daily briefing on Tuesday that he was working with governors in New Jersey and Connecticut on a plan to restart life once the crisis subsides.

Cuomo said that the closures of businesses and schools and other social distancing measures were having the intended impact and urged continued compliance, especially as New York City braces for the possible peak to hospitalizations this week.

“Our behavior affects the number of cases,” said Cuomo. “They are not descending on us from heaven.”

The 731 new deaths on Monday marked an increase from the prior day’s 599 new deaths, while new hospitalizations nearly doubled to 656, contradicting a trend of the past few days which Cuomo had touted as a possible “flattening of the curve”.

But Cuomo cautioned against reading too much into one day of data and stressed three-day averages, which still showed a downward trend in the stress on the state’s hospitals. The governor also pointed to a daily drop in admissions to intensive care units and a fall in intubations as encouraging signs.

Cuomo said health officials have developed an antibody testing regimen that was approved by the U.S. Department of Health and Human Services for use in the state, and said that regulators were working to bring it up to scale.

The test, Cuomo said, would determine whether a person has developed antibodies from contracting and resolving the virus, and would be part of a larger plan aimed at getting people back to work and to school.

“That’s why you would have the antibodies for the virus – that would mean that you are no longer contagious, and you can’t catch the virus because you have the antibodies in your system,” the governor said.

“You are not going to end the virus before you start restating life.”

(Reporting by Nathan Layne in Wilton, Connecticut and Maria Caspani and Stephanie Kelly in New York; Editing by Lisa Shumaker)