Enlarge / Florida Surgeon General Dr. Joseph Ladapo speaks during a press conference at Neo City Academy in Kissimmee, Florida. (credit: Paul Hennessy/SOPA Images/LightRocket via Getty Images)

A sixth student at Florida's Manatee Bay Elementary School outside of Fort Lauderdale has a confirmed case of measles, health officials announced late Tuesday. However, health officials are not telling unvaccinated students who were potentially exposed to quarantine.

The school has a low vaccination rate, suggesting that the extremely contagious virus could spark a yet larger outbreak. But in a letter sent to parents late Tuesday, Florida Surgeon General Joseph Ladapo—known for spreading anti-vaccine rhetoric and vaccine misinformation—indicated that unvaccinated students can skip the normally recommended quarantine period.

The letter, signed by Ladapo, noted that people with measles can be contagious from four days before the rash develops through four days after the rash appears. And while symptoms often develop between 8 to 14 days after exposure, the disease can take 21 days to appear. As such, the normal quarantine period for exposed and unvaccinated people, who are highly susceptible to measles, is 21 days.

Face of boy after three days with measles rash. (credit: CDC)

Florida health officials on Sunday announced an investigation into a cluster of measles cases at an elementary school in the Fort Lauderdale area with a low vaccination rate, a scenario health experts fear will become more and more common amid slipping vaccination rates nationwide.

On Friday, Broward County Public School reported a confirmed case of measles in a student at Manatee Bay Elementary School in the city of Weston. A local CBS affiliate reported that the case was in a third-grade student who had not recently traveled. On Saturday, the school system announced that three additional cases at the same school had been reported, bringing the current reported total to four cases.

On Sunday, the Florida Department of Health in Broward County (DOH-Broward) released a health advisory about the cases and announced it was opening an investigation to track contacts at risk of infection.