FORT MYERS, Fla. (WINK) — The measles outbreak in Southwest Florida continues to grow, with new data showing the virus is still spreading — primarily in Collier County.

Data released on Thursday by the Florida Department of Health shows measles is affecting younger age groups for the first time this year.

Data shows Collier and Lee Counties have reported 75 confirmed measles cases as of Feb. 21, a nearly 18% increase from the 62 cases reported as of Feb. 14.

Of the recently confirmed cases:

73 are in Collier County

Two are in Lee County

“The numbers are going up because the number of folks that are vaccinated has gone down,” Rosemary Higgins, a trained pediatrician and associate vice president for research and sponsored programs at Florida Gulf Coast University, said. “It’s concerning, and we may see more cases as we go forward.”

Data shows an additional 10 cases in Collier County are considered ‘probable,’ meaning those patients are showing symptoms consistent with measles. While some confirmed cases are no longer contagious, the rising numbers show the measles outbreak remains active.

The most recent data also shows the outbreak has now affected a younger age group. Higgins said she believes younger age groups are being affected by lower vaccination rates.

“If people have measles and they expose unvaccinated folks, it’s highly, highly contagious,” she said. “So, if you’re not vaccinated, the odds are you’re going to get it. Probably 80 to 90-plus chance if you’re exposed to somebody.”

Data shows one probable case involving a child in Collier County aged 5 to 9. It’s the first time this year that measles has been reported in that age range in Southwest Florida.

Higgins said herd immunity requires vaccination rates of around 95%, but many communities are now falling short of that threshold.

Most of the recently confirmed cases are among teenagers and young adults, data shows:

Measles vaccines are typically given between 12 and 15 months of age, with additional doses later in childhood. Health experts say younger children often become infected after exposure to older family members or others in the community.

Higgins says measles typically develops eight to 12 days after exposure, but infected people can spread the virus before they realize they are sick. 

Symptoms often include:

Fever

Cough

Runny nose

Red eyes

A blotchy red rash

Serious symptoms could include pneumonia and brain swelling, known as encephalitis, which occurs in about one in 1,000 cases, according to Higgins. School-age children and young adults are at risk of experiencing serious symptoms, but the highest risk is among infants, pregnant women, and older adults, according to health experts.

No confirmed cases have been reported this year in Charlotte, Hendry, Glades, or DeSoto counties.

WINK News will continue to track the measles outbreak and provide updates as new data becomes available.