Public health officials in Texas acknowledged the possibility that someone else could contract Ebola, widening their search Thursday for 100 individuals possibly exposed to the first Ebola patient diagnosed in the U.S.

According to the Dallas County Health and Human Services, this group of 100 potential contacts were identified by the group of 12-18 people who first came into contact with the infected man, identified as Thomas Eric Duncan.

“It’s constantly evolving, people are going to get added, people are going to get dropped off,” Dallas County Health and Human Services spokeswoman Erikka Neroes told FoxNews.com. “How many people will contract Ebola, we don’t know that. [There’s a] possibility someone may. We’re out there working to make sure [it’s] under control.”

Five schools in the Dallas Independent School District sent letters home with parents informing them that a student at the individual schools may have been in contact with the Ebola patient. The schools included Conrad High, Hotchkiss Elementary, Dan D. Rogers Elementary and Tasby Middle schools. Letters also went home to parents at Lowe Elementary because it is next door to Tasby.

The five students— none of whom showed symptoms— were told to stay at home away from school. The letters noted that “there is no imminent danger to your child.”

The 12-18 person primary contact group is being checked on a daily basis— with their temperatures being checked twice daily— by public health officials. The secondary group of 100 people are being monitored in the form of awareness and education of signs and symptoms. It is not known whether all 100 contacts have been reached out to yet.

“If they haven’t been contacted yet, they will be,” Neroes said.

The Centers for Disease Control and Prevention (CDC) and Dallas County have 20 public health  officials on the ground, monitoring contacts, in addition to staff answering phones and fielding questions.

There have been no reports of symptomatic individuals in Dallas County.

“The important thing is none of the people on any of the lists show any signs or symptoms of Ebola as of yet,” Neroes said. “We all know by now, you can’t catch Ebola without any contact with someone while they are symptomatic, according to the CDC.”

The family of Duncan is under orders to stay at home, in isolation for 21 days, the duration of the Ebola virus incubation period. If they have not become symptomatic after that time, they no longer have to remain in isolation, Neroes said.    

Sally Nuran, manager of the Ivy Apartments where Duncan was visiting family, said during a press conference Thursday that health officials alerted her of the Ebola case on her property late Monday night. She confirmed that the lease for that particular unit lists one adult and two children, but said she does not know how many people are currently occupying the space.

As part of the monitoring process, the CDC has quarantined the family inside the unit, with strict instructions not to leave the apartment or even step out on the porch, according to Nuran. The family was set to move out of the apartment when their lease expired on September 30.

According to Dr. David Lakey, commissioner of Texas Department of State Health Services, the family’s apartment will be cleaned by a cleaning company.

“The house conditions need to be improved,” Lakey said in a press conference Thursday. “We have been working to identify an entity that will go out and there and do cleaning— there has been hesitancy… but we have identified and that will take place today.”

Lakey also noted that there is a local law enforcement agent monitoring the apartment.

The complex is home to residents of many different nationalities and translators have been on hand to distribute information in at least eight different languages, according to Nuran, who said she’s working with the CDC and other government agencies to educate residents about the current situation.

Fliers were placed on residents’ doors in the apartment complex Wednesday night and more translated fliers will be handed out during a community meeting Thursday, according to Nuran, who said that language barriers have made it difficult to disseminate information. Nuran added that all common areas have been disinfected by the CDC.

According to Neroes, the number of those potentially exposed to Ebola will continue to change as the situation evolves.

A Dallas emergency room sent Duncan home last week, even though he told a nurse that he had been in disease-ravaged West Africa. The decision by Texas Health Presbyterian Hospital to release Duncan could have put others at risk of exposure to Ebola before the man went back to the ER a couple of days later when his condition worsened.

The patient explained to a nurse last Thursday that he was visiting the U.S. from Africa, but that information was not widely shared, said Dr. Mark Lester, who works for the hospital's parent company.

Hospital epidemiologist Dr. Edward Goodman said the patient had a fever and abdominal pain during his first ER visit, not the riskier symptoms of vomiting and diarrhea. Duncan was diagnosed with a low-risk infection and sent home, Lester said.

Texas Health Presbyterian Hospital is reviewing how the situation would have been handled if all staff had been aware of the man's circumstances. "(Hospital officials) told me that is something they are looking into," spokeswoman Candace White said.

David Wright, regional director of the U.S. Centers for Medicare & Medicaid Services, wouldn't say if the hospital was under investigation. Wright said that in cases they do handle, federal investigators examine if a hospital complied with a "reasonable physician standard" in deciding whether to admit a patient with a potential medical emergency.

But the diagnosis, and the hospital's slip-up, highlighted the wider threat of Ebola, even far from Africa.

"The scrutiny just needs to be higher now," said Dr. Rade Vukmir, a spokesman for the American College of Emergency Physicians.

Duncan has been kept in isolation at the hospital since Sunday. He was listed in serious but stable condition.

The Associated Press and FoxNews.com's Nicole Kwan contributed to this report.