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 eight 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.

"Because of the high likelihood of infection, it is normally recommended that children stay home until the end of the infectious period, which is currently March 7, 2024," Ladapo's letter states, adding that the date could change as the situation develops. "However, due to the high immunity rate in the community, as well as the burden on families and educational costs of healthy children missing school, [the health department] is deferring to parents or guardians to make decisions about school attendance."

Local media outlets reported that, on Tuesday, more than 200 of the school's 1,067 students were absent.

The measles cluster began Friday when a third grader, who had not recently traveled, was diagnosed with the vaccine-preventable illness. Over the weekend, three additional cases were identified, leading the local health department to release a health advisory. Two additional cases were identified this week. It's unclear if all six children are unvaccinated.

According to a county vaccine study, only 89.31 percent of the school's students were vaccinated in the 2023/2024 school year, suggesting that around 114 students are susceptible due to their vaccination status.

The measles virus spreads easily through respiratory transmission and can linger in air space for up to two hours after an infected person has been in an area. Among people susceptible to the virus—those who are unvaccinated or have compromised immune systems—up to 90 percent will become infected upon exposure. People who are fully vaccinated, meanwhile, are considered protected. Two doses of the Measles, Mumps, and Rubella (MMR) vaccine are 97 percent effective at preventing the disease.

Measles symptoms include high fever, runny nose, red and watery eyes, and a cough, as well as a telltale rash that develops after initial symptoms. About 1 in 5 unvaccinated people with measles are hospitalized, according to the Centers for Disease Control and Prevention, while 1 in 20 infected children develop pneumonia and up to 3 in 1,000 children die of the infection.