The Nassau County Department of Health is warning Long Islanders that there was a “potential exposure to measles” at the Cohen Children’s Medical Center Emergency Department waiting room and treatment area earlier this week.

Officials say the exposure took place from 6:45 p.m. on Wednesday, March 20 until 3:30 p.m. Thursday, March 21.

According to a news release sent out Sunday: “Cohens Children’s Medical Center is contacting patients who visited the emergency department at the time of the potential exposure and has identified patients who are at high risk who may require timely treatment."

It also said the best way to prevent measles is to be vaccinated.

Northwell Health sent a statement to News 12. It says, "Cohen Children’s Medical Center, the largest Level I Pediatric Trauma Center in New York State, is working closely with state and local health officials after it was determined that a patient who presented at the emergency department was found to have measles. The patient was isolated and admitted on March 21 and is currently in stable condition. Measles is a highly infectious viral respiratory illness for the unvaccinated. "We are contacting patients who visited the emergency department at the time of the potential exposure and have identified patients who are high risk and may require timely treatment."

The health department says the child is under 5 years old. Officials say the child was admitted on Thursday in stable condition.

The child has since been discharged from Cohen's Children's Medical Center, according to a Northwell Health spokesperson.

This is the third case of measles reported in Nassau County since 2019.

News 12 reported that on Friday a Nassau County resident had been confirmed to have the third measles cases in the state this year, according to the New York State Department of Health (NYSDOH).