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Some nervous Dallas parents picked up their children early from school Wednesday after learning that five students attended class after possibly being exposed to the first Ebola patient diagnosed in the U.S.

School administrators urged calm. None of the children have shown symptoms and are now being monitored at home, where they are likely to remain for three weeks, Dallas Independent School District Superintendent Mike Miles said.

But Marcie Pardo and other parents left L.L. Hotchkiss Elementary indicating that they might take no chances and keep their children home the rest of the week.

"Kids pretty much touch everything. Not everyone washes their hands," Pardo said. "It's the contagious part that gets me worried."

Ebola isn't contagious until symptoms appear, and then it can spread only by close contact with a patient's bodily fluids. Pardo said that knowledge makes her feel better — but her 8-year-old daughter, Soriah, still left school early along with her cousin.

Tucked in a quiet neighborhood of tree-lined streets, Hotchkiss is one of four campuses in Dallas that Miles says the five students attended. He said the district is taking an "abundance of caution" and would add more health workers to keep watch for symptoms among students.

The district also planned to deploy more custodial workers to the campuses, which include another elementary school, two middle schools and a high school.

"The students didn't have any symptoms, so the odds of them passing on any sort of virus is very low," Miles said.

Nonetheless, Texas Gov. Rick Perry acknowledged that "parents are being extremely concerned about that development." Health officials say the five children are among 12 to 18 people being monitored after exposure to the man, who was listed in serious but stable condition at Texas Health Presbyterian Hospital.

It was not exactly clear how the Ebola patient knew the children, but his sister said he had been visiting with family including two nephews.

A pack of police officers and reporters outside Hotchkiss only added to Maria Vargas' nerves as she picked up her daughter Kailey. She said she didn't' know much about Ebola aside from that "it was very bad," and was told by a teacher that class was still on for Thursday.

"I'm worried. But I asked her, 'We have to bring her tomorrow?' She said yeah," Vargas said.

The schools are in and around a part of Dallas known as Victory Meadow, one of the city's most diverse neighborhoods. Officials say one challenge will be getting information out in a part of town where 33 different languages are spoken, and that they would go door-to-door if necessary.

Ebola is believed to have sickened more than 7,100 people in West Africa, and more than 3,300 deaths have been linked to the disease, according to the World Health Organization. Symptoms can include fever, muscle pain, vomiting and bleeding, and can appear as long as 21 days after exposure to the virus.

Following her 4-year-old grandson down the sidewalk outside Hotchkiss, Cookie Deckard said she wasn't overly worried. But she wished the schools would at least reveal the ages of the affected students, and because her grandson is just getting over being sick, she said she'll consider keeping him home.

"It's definitely a concern," Deckard said. "It's better to be safe than sorry."