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A Houston nurse is no longer employed after she posted on social media about a young patient with measles, Texas Children’s Hospital said Thursday.

The nurse also made anti-vaccine comments, something that alarms public health officials wary of anything that might feed the small but vocal vaccine skeptic movement.

“A patient treated at Texas Children’s Hospital West Campus tested positive for measles. This is a highly contagious, vaccine-preventable infection. We know vaccination is the best protection against measles,” the hospital said in a statement.

“We were also made aware that one of our nurses posted protected health information regarding a patient on social media,” the hospital added.

“We take these matters very seriously, as the privacy and well-being of our patients is always a top priority. After an internal investigation, this individual is no longer with the organization.”

The hospital did not identify the nurse. A Facebook user who alerted Texas Children’s to the post said she was shocked by what the nurse had said, and copied a screenshot of it to the Texas Children’s Facebook page.

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“The kid was super sick. Sick enough to be admitted to the ICU and he looked miserable,” the nurse posted to an anti-vaccine Facebook page. But she said she still opposed vaccines.

This shocked Dr. David Persse, director of the Houston Health Department. “She is one of the few people who has seen firsthand how devastating these diseases can be, and she has still taken this position against vaccines," Persse said in an interview.

He pointed out that many studies have established the safety of vaccines, and that medical professionals should be educated about the facts.

“You have a greater risk of being struck by lightning than you do of having a serious adverse event to a vaccine," Persse said.

Measles has been eliminated in the United States through vaccination, but every year, cases are imported from other countries. People who are not vaccinated or who are incompletely vaccinated can be infected and carry the virus with them. It will spread if there are pockets of other unvaccinated people.

Europe is experiencing its largest number of measles cases in a decade, and the Centers for Disease Control and Prevention has notified travelers about the risks of traveling to affected areas.

Persse said his department is helping track everyone that the child might have been in contact with while infectious. Measles is one of the most infectious viruses known, and people can spread it before they begin showing symptoms.

Measles killed nearly 90,000 people globally in 2016, according to the World Health Organization. Nine out of 10 people who have not been vaccinated will develop an infection if they are exposed to someone with the virus, and can even become infected if they walk into a room where an infected person has been.

So when a case of measles is identified, health officials work to track down anyone who could have been exposed.

“We got lucky this time,” Persse said. He said the child was not in contact with many people other than his family before he was isolated in the hospital.

The Facebook user who revealed the nurse’s posts said she used an alias on social media and did not wish to be identified for fear of retaliation by members of the anti-vaccine movement, who often attack medical professionals when they speak out about the safety of vaccines.

Her post was taken down on Thursday afternoon.