Flu cases in N.J. are double what they were this time last year. A new variant may be to blame.

Influenza is sickening thousands of people in New Jersey and shows no signs of slowing down, according to state data released Friday.

New Jersey reported 12,211 total influenza, or flu, cases for the week ending Dec. 27 — more than double what it reported the same time last season.

Flu-associated emergency department visits that resulted in hospitalization and outpatient visits have also exceeded last season’s numbers. Most of the hospitalizations have been reported in people 65 years and older, according to state data.

The flu also contributed to a rise in absenteeism in K-12 schools in December.

The flu is nothing new. It’s associated with millions of illnesses and hospitalizations each year, with the virus typically spreading in the U.S., beginning in October and peaking in late winter.

This year, however, there’s a new strain of influenza A(H3N2) called subclade K , which is circulating globally.

Data from South America — which predicts the effectiveness of the 2025–2026 Northern Hemisphere flu vaccine — suggests this season’s vaccine may be less effective against influenza A-related infections. Officials say that could be contributing to the sharp increase in flu cases.

Among 275 influenza A(H3N2) viruses collected since Sept. 28, 2025, that underwent additional testing at the Centers for Disease Control and Prevention, 89.5% belonged to subclade K.

However, people who received a flu shot were still less likely to get severely ill than those who didn’t. The 2025 Southern Hemisphere seasonal influenza vaccine reduced influenza-associated hospitalizations by 49.7%, according to the CDC.

Most people who become ill with the flu recover without serious complications. However, the following groups are more likely to develop severe complications:

Young children.Pregnant women.People with certain chronic health conditions, such as asthma, diabetes or heart disease.People 65 years and older.

During the 2024–2025 flu season, 38,000 people across the U.S. died from flu complications, according to the CDC.

Of those who died, 288 were children, the highest number in a single season since the 2009-2010 pandemic. The majority of deaths were among children who were not fully vaccinated against the flu.

A total of eight flu-associated pediatric deaths have occurred during the 2025-2026 season.

Doctors say vaccination isn’t guaranteed to prevent the flu, but it will reduce the severity of illness.

Everyone 6 months and older is encouraged to get an annual flu vaccination, per CDC guidelines. This has been the agency’s recommendation since 2010, according to its website.

In addition to the flu, test positivity increased in December for several respiratory viruses, including COVID-19, RSV, and Rhinovirus.