Westchester County Executive George Latimer said two families traveled to Florida prior to the event and two individuals came back with coronavirus
One of the individuals attended the Horace Greeley High School drive-in graduation ceremony held on June 20 at Chappaqua Train Station, began showing symptoms after the event and tested positive for coronavirus four days later.
13 people who attended that event have tested positive, Latimer said.
In addition to the graduation ceremony, the student participated in a non-school related "Field Night" event on June 20, which was also attended by juniors and seniors and students from surrounding school districts.
Latimer said not all positive cases are in New Castle and at least one of the cases is located in the neighboring town of Mt. Pleasant.
"Of the 14 that are positive these people are all inter-related by where they were or by personal association, but that's what constitutes a cluster," Westchester Co. Health Commissioner Dr. Sherlita Amler said.
Officials say all individuals who have tested positive are currently self-isolating.
Any individuals who attended the graduation ceremony, Field Night, or any other events associated with the graduation should extend their quarantine period until July 5th, officials urged.
Latimer urged people to wear masks and practice social distancing at all events, including Fourth of July gatherings this weekend.
"I'm concerned that we are taking all the precautions to try and be safe and there are people you know that really don't care," resident Andrea de Friutos said.
Governor Andrew Cuomo has consistently praised New Yorkers for their social-distancing and mask-wearing efforts, yet he knows a small percentage of rule-breakers can lead to a big problem. He says what happened in Chappaqua represents more than just a lack of self-control.
"Local governments need to do the enforcement. They need to do the compliance, Cuomo said.
"Two officers were going through the crowd. They were putting reminders to everybody. We did not issue any summonses. Most people were complying," Lt. James Dumser of the New Castle Police Department said.
The county executive says there's a limit to what authorities can do to make sure people take the necessary precautions.
"There are not enough police in the world to come to your front door to make you do what you know is right," Latimer said.
Chappaqua Central School District tweeted out photos of the drive-in high school graduation, where 343 seniors graduated.
Even Bill and Hillary Clinton had a video message congratulating Class of 2020, which is described as a "message from two of your neighbors."
The New York State Department of Health and the Westchester County Health Department are working with officials from Horace Greeley to identify all individuals who attended the graduation ceremony and any subsequent gatherings where they may have been exposed. The New York State Contact Tracing Program will be reaching out to identified individuals and anyone who attended the ceremony or subsequent gatherings should get tested.
On June 14, New York State DOH issued guidance to ensure any district that decides to host a graduation ceremony adheres to appropriate protective measures including social distancing, limitations on number of attendees, wearing face coverings, and other precautions. Part of the comprehensive public health response will be to determine whether the guidance had been followed.
As part of their public health outreach, the State and County DOH encourage testing for anybody who attended the graduation ceremony or the Field Night event and may have come in contact with an infected individual.
A Tri-State travel quarantine was announced by Cuomo on June 18, including New Yorkers returning home from elsewhere.
Right now travelers from eight states are required to quarantine for 14 days if they come to New York, New Jersey, or Connecticut.
Those states are Alabama, Arkansas, Arizona, Florida, North Carolina, South Carolina, Utah, and Texas.
RELATED: How the NY, NJ and CT quarantine will work
The governor also issued a new executive order that makes New York employees who voluntarily travel to high-risk states after June 25 ineligible for COVID-19 paid sick leave.
"New Yorkers have controlled the spread of this unprecedented virus by being smart and disciplined, and our progress to date is illustrated by the current low numbers of new cases and hospitalizations," Cuomo said. "But as we are seeing in other states who reopened quickly, the pandemic is far from over and we need stay vigilant. We're prepared to do the aggressive testing and contact tracing required to slow and ultimately control any potential clusters of new cases like the one in Westchester County. If we are going to maintain the progress we've seen, we need everyone to take personal responsibility - that's why I'm issuing an executive order that says any New York employee who voluntarily travels to a high-risk state will not be eligible for the COVID protections we created under paid sick leave."
For information about testing, please contact your local healthcare provider, or click here.
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