TRENTON — The progress New Jersey has seen in the past three months in "flattening the curve" of the coronavirus may slowly be unraveling as a result of a series of packed house parties, most involving teens and young adults in the suburbs.

Gov. Phil Murphy on Wednesday again chastised young people for throwing these parties, which have resulted in dozens of known cases of COVID-19, adding that the state has counted 2,000 new cases in the past four days — bringing New Jersey back to where it was a month ago in terms of new cases.

"We can't go backwards. We can't afford to go backwards," Murphy said on a day that the state reported 489 new cases and added 18 deaths to a toll approaching 14,000.

“We simply cannot continue to have crowded house parties. They are not safe – period. They are how coronavirus gets passed around more efficiently. They put the hard work we’ve all undertaken together since March at risk of being undone.”

Among the massive private gatherings that raised alarm:

  • A series of house parties in Middletown have been linked to 55 cases of coronavirus in 14- to 19-year-olds.
  • Parties on Long Beach Island resulted in 35 lifeguards in Harvey Cedars and Surf City getting sick.
  • A Cape May County graduation party in June resulted in 39 cases among New Jersey and Pennsylvania residents ages 16 to 23.
  • A graduation party in Westfield resulted in 17 cases.
  • A Father's Day celebration in Essex County resulted in three cases.
  • At Rutgers, 15 football players have tested positive.

Health Commissioner Judith Persichilli said the percentage of COVID-19 cases among people ages 18 to 29 has increased from 12% in April to 22% in June to as much as 33% in the first three weeks of July.

Younger adults are less likely to develop the most serious complications from COVID-19 or die but they are more likely to spread it to more vulnerable adults, especially when they do not have or are not aware that they have symptoms.

On Sunday in Jackson, a "mansion party" to celebrate Liberian Independence Day brought out 700 people. Murphy said it took the entire township police force on hand plus state troopers and officers from neighboring department to disperse the crowd.

Township police said neighbors reported that 500 people had been at another party at the same house at 84 Mill Pond Road the night before. The owner, Yaakov Weiss, 40, along with the party organizers, Patience Guanue, 23, and Alicia Hinneh, 22, both of Newark, were charged with violating the executive order limiting gatherings. Indoor gatherings are capped at 100 people or 25% of a room's normal capacity, whichever is less, while outdoor gatherings can have no more than 500 people.

Elsewhere, police broke up a gathering of 400 people at a house in Brick on July 20.

Gatherings at the Jersey Shore also have been linked to a growing number of cases in neighboring Pennsylvania, were nearly a quarter of cases in Philadelphia were linked to travel outside of their state, most commonly the Shore.

Murphy said the easier spread of the virus indoors is the reason why he "hit pause" on reopening indoor dining and gyms.

Persichilli said that if people have gatherings at their homes, they should provide guests with hand sanitizer, designate a single person to pass out food and keep a contact sheet listing all guests in order to help contact tracers later in the event of an outbreak linked to the gathering.