Infectious disease

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Measles erupts in Florida school where 11% of kids are unvaccinated

outbreak potential —

Over 100 children at the school are susceptible to virus.

A child with measles.

Enlarge / A child with measles.

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.

At Manatee Bay Elementary School, the number of children at risk could be over 100 students. According to a Broward County vaccine study reported by the local CBS outlet, only 89.31 percent of students at Manatee Bay Elementary School were fully immunized in the 2023/2024 school year, which is significantly lower than the target vaccination coverage of 95 percent. The school currently has 1,067 students enrolled, suggesting that up to 114 students are vulnerable to the infection based on their vaccination status.

Measles is one of the most contagious viruses known. It spreads via respiratory and airborne transmission. The virus can linger in air space for up to two hours after an infected person has been in an area. People who are not vaccinated or have compromised immune systems are susceptible, and up to 90 percent of susceptible people exposed to the virus will become infected. Measles symptoms typically begin around eight to 14 days after exposure, but the disease can incubate for up to 21 days. The symptoms begin as a high fever, runny nose, red and watery eyes, and a cough before the telltale rash develops. Infected people can be contagious from four days before the rash develops through four days after the rash appears, according to the Centers for Disease Control and Prevention. About 1 in 5 unvaccinated people with measles is hospitalized, the CDC adds, while 1 in 20 infected children develop pneumonia and up to 3 in 1,000 children die of the infection.

Those who are not immunocompromised and are fully vaccinated against measles (who have received two doses of the Measles, Mumps, and Rubella (MMR) vaccine) are generally not considered at risk. The two doses are about 97 percent effective at preventing measles and protection is considered to be life-long.

The DOH-Broward said it is now “identifying susceptible contacts that may be candidates for post-exposure prophylaxis through MMR or immunoglobulin.”

While the risk of measles is generally low in the US—the country declared it eliminated in 2000—the threat of large outbreaks is growing as vaccination rates slip. Many cases in the US are linked to travel from countries where the virus still circulates. But, if a travel-related case lands in a pocket with low vaccination coverage, the virus can take off. Such was the case in 2019, when the country tallied 1,274 measles cases and nearly lost its elimination status.

Health officials typically consider vaccination coverage of 95 percent or greater to protect from ongoing transmission. In the years since the COVID-19 pandemic began, vaccination rates among US kindergartners have slipped to 93 percent, and vaccination exemptions reached an all-time high in the latest data from the 2022-2023 school year. There are now at least 10 states that have vaccination exemption rates above 5 percent, meaning that even if every non-exempt child is vaccinated, those states will not have enough coverage to reach the 95 percent target.

The CDC has tallied 20 measles cases in the US so far this year. But that is the tally as of February 15; it does not include any of the Florida cases reported since Friday. In 2023, there were 58 measles cases reported to the CDC.

This story was updated to include additional information about measles infection outcomes.

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Measles is “growing global threat,” CDC tells doctors in alert message

Alert —

Since December, there have been 23 measles cases in the US, including two outbreaks.

A baby with measles.

Enlarge / A baby with measles.

The Centers for Disease Control and Prevention is putting clinicians on alert about the growing risk of measles cases and outbreaks amid a global surge in transmission.

In an outreach message sent Thursday, the CDC told clinicians to look out for patients who have a rash accompanied by a fever and other symptoms of measles, as well as patients who have recently traveled to countries with ongoing measles outbreaks.

Between December 1, 2023, and January 23, 2024, there have been 23 confirmed measles cases in the US, including seven direct importations by international travelers and two outbreaks with more than five cases each, the CDC noted. Most of the cases were in unvaccinated children and teens.

Measles outbreaks in the US are typically sparked by unvaccinated or undervaccinated US residents who pick up the infection abroad and then, when they return, transmit the disease to pockets of their communities that are also unvaccinated or undervaccinated.

Globally and in the US, vaccination rates against measles—via the measles, mumps, and rubella vaccine (MMR)—have fallen in recent years due to pandemic-related health care disruption and vaccine hesitancy fueled by misinformation.

“The increased number of measles importations seen in recent weeks is reflective of a rise in global measles cases and a growing global threat from the disease,” the CDC’s outreach message, titled “Stay Alert for Measles Cases,” read.

According to data from the World Health Organization, the European region saw an over 40-fold rise in measles cases in 2023 as compared with 2022. The region tallied over 42,200 measles cases last year, compared with just 941 in 2022.

This week, the WHO reported a rapid escalation of measles cases in Kazakhstan (which the WHO considers part of the European region). Kazakhstan has recorded the highest incidence of measles cases in the region, with 13,677 cases in 2023. That corresponds to over 639 cases per million in the population. In the news release Tuesday, Kazakhstan’s health minister reported that there are “currently 2,167 children in hospital with measles, 27 of them in a serious condition.”

The outbreak is largely spurred by unvaccinated children who missed their routine immunizations during the pandemic. Sixty-five percent of the reported measles cases are in children under age 5, the WHO noted. The country is now trying to catch children up on their vaccines to curb the outbreak.

“Measles is highly infectious, but fortunately, can be effectively prevented through vaccination,” WHO’s Regional Director for Europe, Hans Henri P. Kluge, said in the news release. “I commend Kazakhstan for the urgent measures being taken to stop the spread of this dangerous disease.”

Meanwhile, measles is flaring up in many other places. Last week, the UK Health Security Agency warned of the potential for an ongoing measles outbreak to spread. As of January 18, there were 216 confirmed cases and 103 probable cases in the West Midlands region since October 2023. Authorities warned that any areas with low MMR vaccination rates are at risk of an outbreak.

The vast majority of Americans have received their MMR vaccines on schedule. In this case, the two standard, recommended doses are considered 97 percent effective against measles, and the protection is considered for life. But anyone who is unvaccinated or undervaccinated is at high risk of infection in the event of an exposure. The virus can linger in air space for up to two hours after an infected person leaves the area, the CDC notes, and is highly infectious—up to 90 percent of unvaccinated people exposed will fall ill. Once infected, people are infectious from four days before the telltale measles rash develops to four days afterward.

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