Editor's note: This story has been updated throughout.

Fear over possible exposure to Ebola has triggered campus closures in some Texas school districts and additional safety measures at many more in the almost three weeks since a Dallas hospital diagnosed the first case of Ebola in the United States.

In Central Texas, the Belton Independent School District decided to shutter three campuses Thursday and Friday because students had been on the same flight with a recently infected nurse. Northeast of Dallas, the Royse City school district announced it would not hold classes at two schools Friday for a voluntary cleaning "out of an abundance of caution" after learning that someone who lived with a student there worked with one of the health care providers who contracted the virus.

Four other districts, all in North Texas — Eagle Mountain-Saginaw, Grapevine Colleyville, Garland and Lewisville — have identified employees or relatives of students who traveled on that flight and issued notices to parents saying they would thoroughly clean affected campuses but would not cancel school.

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And at least two districts, Abilene and Lubbock, have updated enrollment procedures for new students to include questions about recent travel to West African countries. In the Dallas Independent School District, the five campuses with children who had contact with the first Ebola victim have installed fever scanners.

Though Texas schools are relying on the guidance of health officials to determine the level of risk to their communities, they are making decisions like whether to cancel classes, give notice to parents or change health screening policies largely on their own once they receive that information.

"It’s local decision, almost always, and we support that. They know what’s best," said Lauren Callahan, a spokeswoman for the Texas Education Agency. “We want parents to know our school districts are doing what they believe is best for their students. We are monitoring the situation here, and superintendents are doing a good job."

Two nurses who treated Thomas Eric Duncan, a Liberian man who was in Dallas when he fell ill with Ebola, have tested positive for the disease since Duncan died on Oct. 8. Federal health officials are now in the process of tracking down passengers who were on two flights one of the nurses took between Cleveland and Dallas before she became sick. They have emphasized such measures are precautionary, because the virus can only be transmitted through direct exposure to the bodily fluids including blood, sweat, saliva, vomit and diarrhea of someone who is showing symptoms.

Because of that, medical experts also said the probability of Ebola entering public schools is very low.

“The biggest threat to Texas school children is all the regular stuff. Influenza, pertussis. They are much more likely to be exposed to pertussis than they are to Ebola,” said former state Rep. Mark Shelton, R-Fort Worth, a physician who specializes in pediatric infectious diseases. “I would be surprised if Ebola made its way into public schools.”

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A letter the Dallas County Medical Society, which represents 7,000 doctors, sent to school officials Friday afternoon recommended against closures. It also advised against measures like keeping the children of asymptomatic parents home or "deep cleaning" schools, which it said gave the wrong impression about the risks of contracting the disease.

"Keeping all schools open, including schools that have children of parents who are being monitored, presents no risk to students or teachers and sends an important message of allaying fears in the community," reads the letter, signed by 18 doctors. "School closures, especially given the significant ramifications that would have on our community, are NOT an effective way to prevent Ebola infections."

Margaret Ryan, the president of the Texas School Nurse Organization, said she had confidence that school nurses in the state had the training to follow the proper protocol if a student had any questionable symptoms.

But she pointed out that Texas law does not require schools to employ nurses.

“Some of the small districts, and some of the districts that don’t have nurses, that might be a concern, whether they have adequate information, it just depends on your school districts and if they’ve gone to the CDC website to get information or not,” she said of the Centers for Disease Control and Prevention. 

As the virus is contained, the biggest challenge for school districts may be how to make up missed school days and address lagging attendance rates as parents keep their children at home out of concern they may come into contact with it.

At an Eagle Mountain elementary school, about 40 percent of students stayed home despite assurances the district had thoroughly cleaned the campus twice, according to local reports. In Dallas, the Highland Park elementary school attended by the children of a county judge who has spent time with the family of the first Ebola victim sent home a letter to parents saying there was no risk to students after absentee rates surged.

Because the Texas Education Agency has received so many calls and emails from school officials on the issue, it plans to send a letter to school administrators clarifying state attendance law, Callahan said.

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"We are in touch, and our districts very well equipped to handle the situation. They are making decisions and keeping us informed about what is going on," she said. 

This story was produced in partnership with Kaiser Health News, an editorially independent program of the Henry J. Kaiser Family Foundation, a nonprofit, nonpartisan health policy research and communication organization not affiliated with Kaiser Permanente.