New York is reporting the highest number of flu hospitalizations recorded in a single week, the state's health department said on Friday.

During the week ending Dec. 27, 4,546 people were hospitalized with flu, a 24% increase from the 3,666 who were hospitalized the previous week, according to data from the New York State Department of Health (NYSOH)

It comes after the state reported a record-breaking number of flu cases in a single week with 72,133 infections during the week ending Dec. 20.

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NYSDOH issued a declaration last month stating influenza is prevalent in New York, which requires health care facilities and agencies to ensure any staff who have not received this year's flu vaccine wear masks in any areas where patients and residents may be present.

"We are having a more severe flu season than prior years, almost 1,000 more people were admitted to a hospital during this most recent seven-day period compared to the prior week," Dr. James McDonald, the state's health commissioner, said in a statement on Friday.

Meanwhile, flu activity is also spiking nationwide. The Centers for Disease Control and Prevention estimates there have been at least ​7.5 million illnesses, ​81,000 hospitalizations and ​3,100 deaths from flu so far this season.

New York is one of 20 states recording "very high" levels of respiratory illness activity, according to the latest CDC data.

Public health experts previously told ABC News that many of this season's cases are linked to a new flu strain called subclade K -- a variant of the H3N2 virus, which is itself a subtype of influenza A.

Subclade K has been circulating since the summer in other countries and was a main driver of a spike in flu cases in Canada, Japan and the U.K.

Of the 1,600 flu samples tested by the CDC, roughly ​92% were H3N2. Of those samples, nearly ​90% belonged to subclade K.

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Experts expect flu-like illnesses to continue to climb in the coming weeks after holiday gatherings and colder weather.

Currently, the CDC recommends that everyone aged 6 months and older, with rare exceptions, get a flu vaccine.

The federal health agency states on its website that getting an annual flu shot prevents millions of illnesses and flu-related doctors' visits every year and is especially important for those at higher risk of serious complications.

The flu vaccine is currently available to New Yorkers aged 2 years and older at a health care provider's office or at participating pharmacies while children aged 6 months and older can receive the flu vaccine at a health care provider's office, according to the state health department.

"There is still time to get a flu shot and remember, flu can be treated with antiviral medication if started within 48 hours of symptom onset and your doctor deems appropriate," McDonald said.

ABC News' Youri Benadjaoud contributed to this report.