Feb. 20 (UPI) — Six cases of the measles have now been reported in Florida and have been traced back to a Weston elementary school in what some experts warn could be a rising problem with people being unvaccinated.

The names or other identifiable information about those who have been infected with measles — other than the cases were not travel-related — was not available about the outbreak that was linked to Manatee Bay Elementary School in Broward County.

On Sunday, the county’s Department of Health said it was “investigating multiple cases” of the measles, and “continuously working with all partners, including Broward County Public Schools and local hospitals, to identify contacts that are at risk of transmission.”

Measles — a highly contagious virus which has no cure — symptoms appear seven to 14 days after contact with the virus and typically include high fever, cough, runny nose and watery eyes with a rash that appears 3 to 5 days after first symptoms, according to the Centers for Disease Control.

On Friday, Broward County confirmed that a third-grader with no travel history had been reported as being infected with the virus.

While the disease, itself, was virtually eliminated in the United States by the year 2000, experts say the resurgence of the disease likely is linked to a decline in vaccinations for measles, which was introduced in 1963. It is not clear if those who have recently been infected were vaccinated or not.

Before the measles vaccination was instituted, roughly 500,000 cases were reported annually, with about 500 people who died from it on an annual basis. But deaths by measles increased by 43% globally in 2022 compared to 2021. In 2023, there were 58 cases of measles reported in the United States. Across 11 states as of Thursday were a total of 20 reported cases of the measles.

An epidemiologist and the chief innovation officer at Boston Children’s Hospital told ABC News that it is “very likely” this particular outbreak is due to unvaccinated students given how nearly all previous outbreaks were among those who were unvaccinated.

“This pattern aligns with historical data showing that measles primarily spreads among unvaccinated populations,” said Dr. John Brownstein.

Brownstein added that an outbreak like this is “very concerning” due to the fact measles is “highly infectious that can lead to serious health complications, especially in children and immunocompromised individuals,” he told ABC, adding that it indicates “potential gaps in herd immunity,” which is vital to the prevention of such diseases.