Measles cases that turned up in at least three states this year were linked to visits to Florida, federal and state investigators concluded, shedding light on some of the early infections that have fueled an uptick of the highly contagious virus.

Florida's health department thinks families of the cases earlier this year from Indiana and Louisiana may have crossed paths in the state, according to messages sent between local investigators and the Centers for Disease Control and Prevention through late February.

Louisiana previously said its first two measles cases this year in the New Orleans area had been linked to travel to another state, but declined to say which.

A patient in Ohio this year also was sickened by measles after visiting Florida. That infection had not been directly linked to the other two cases.

"As mentioned, we've had an Ohio case that visited [redacted] Florida as well as a case of our own in the region so definitely curious if there is a connection," Megan Gumke, an epidemiologist for the Florida Department of Health, wrote in a Feb. 21 email.

The emails were obtained by CBS News through a Freedom of Information Act request. 

It is unclear if these measles cases are the same as those the Orlando Sentinel reported last month had been treated by local emergency rooms, in an adult and three young children.

A spokesperson for the Orlando Health system declined to comment, deferring to Florida's health department. Grant Kemp, deputy press secretary for the Florida Department of Health, said it would be misleading to highlight Florida as the epicenter between the measles cases, citing other states also reporting infections.

"When communicable diseases are identified in out-of-state residents, that information is transferred to the state where they reside and are not classified as a Florida case," Kemp said in an email.

The cases treated in Orlando were also "completely unrelated" to an outbreak of measles at an elementary school in Florida's Broward County earlier this year, Kemp said.

The initial case behind the Broward County cases was a 9-year-old child who had not been vaccinated due to a religious exemption, the emails say, soon followed by other suspected measles cases in unvaccinated students at the same school. 

The child had not recently traveled abroad. Ultimately nine cases were reported in Florida's Broward County before state officials declared the outbreak over.

It comes as health officials have stepped up their plea for unvaccinated Americans to get a shot before international travel to protect against measles. The U.S. recently marked an unwanted milestone in this year's measles surge, with more cases in the first three months of 2024 than in all of 2023. 

The CDC says cases have also been reported in Arizona, California, Georgia, Illinois, Maryland, Michigan, Minnesota, Missouri, New Jersey, New York City, Pennsylvania, Virginia and Washington.

Among measles infections reported so far this year, the CDC said March 18 that 93% had been linked to travel outside of the country. 

The agency also on March 13 updated its guidance for international travelers to urge unvaccinated Americans to seek out a shot as early as six weeks before their trip abroad, for any traveler who is at least six months old.

No special vaccination guidance has been published for travelers within the U.S. to states with outbreaks. 

The CDC continues to have longstanding recommendations for everyone starting at 12 months old to get vaccinated against measles. The MMR vaccine, which protects against measles, mumps and rubella, has been widely used for decades and is safe and effective against the once-common illness. 

Officials say the recent uptick in cases underscores the need to catch up on routine shots that were missed during the pandemic. But they also think it so far remains "nowhere close to" the kind of ongoing outbreaks that authorities feared could threaten the U.S. status of having eliminated the virus.

Vaccination rates in the U.S. will likely be enough to prevent a repeat of the deadly waves of infections that claimed hundreds of lives and hospitalized thousands of children every year before the vaccine. The measles virus was declared eliminated in the U.S. in 2000, meaning the country was no longer seeing sustained outbreaks.

However, the agency has also warned that growing outbreaks abroad and gaps of immunity within the U.S. left some communities vulnerable to measles spread.

"Given currently high population immunity against measles in most U.S. communities, the risk of widescale spread is low. However, pockets of low coverage leave some communities at higher risk for outbreaks," the CDC said.

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  • Measles
Alexander Tin

Alexander Tin is a digital reporter for CBS News based in the Washington, D.C. bureau. He covers the Biden administration's public health agencies, including the federal response to infectious disease outbreaks like COVID-19.

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