Texas Governor Rick Perry says health officials are keeping watch on as many as 18 people who came in contact with the first patient to be diagnosed with Ebola in the United States.
They include five schoolchildren. Ambulance workers who brought the patient to the hospital have tested negative.
Those with whom he had contact since arriving in the United States on September 20 will be monitored for at least 21 days - the Ebola virus incubation period. But officials say no other cases are suspected.
The Ebola patient from Liberia, identified as Thomas Eric Duncan, is in isolation in a Dallas hospital. He was listed as serious but stable condition Wednesday.
A hospital official says when Duncan first felt sick he told an emergency room nurse that he had come from Liberia - the epicenter of West Africa's Ebola outbreak - but that information was not shared with hospital officials.
He was sent home with antibiotics, but returned two days later and was admitted.
Stanley Gaye is the head of the Liberian Community Assocation of Dallas-Fort Worth in Texas. He tells VOA the organization is urging local Liberian immigrants to contact the U.S. Centers for Disease Control if they think they might have been exposed to the deadly virus.
"Those that have been in contact with this individual, we ask that they reach out to the CDC and the hospital to make sure they have been - literally be tested, not to be ashamed of it," Gaye said, adding that his organization is sending out that same message to Liberians by text and e-mail.
In serious condition
The patient has been in isolation at Texas Health Presbyterian Hospital in Dallas since Sunday. Mark Lester, an executive with Texas Health Resources, told reporters Wednesday that the patient is in serious but stable condition.
Thomas Eric Duncant is believed to have been infected with the potentially deadly virus in Liberia. He started showing symptoms days after he arrived in Dallas on September 20, reportedly to visit family members.
He is currently being treated at Texas Heath Presbyterian Hospital, is in strict isolation and listed as in serious condition.
That would most likely be friends and family members. In an attempt to reassure the public, officials said no one who flew to the United States on the same plane with the patient is in any danger.
The chief of the U.S. Centers for Disease Control Tom Frieden said there is no doubt authorities will contain the virus, so that it will not spread widely in the U.S.
"We have a seven-person team in Dallas today helping to review that with the family and make sure we identify everyone that could have had contact with him,'' Dr. Thomas Frieden, director of the U.S. Centers for Disease Control and Prevention (CDC), told NBC in an interview.
How Ebola spreads
Ebola spreads though contact with bodily fluids such as blood or saliva, something public health experts say naturally limits its potential to infect others, unlike airborne diseases.
Frieden said experts were monitoring "a handful'' of people
who were potentially exposed, including family members the patient was visiting.
"The team on the ground will review that very intensively to see whether there's any other groups who, out of an abundance of caution, we would want to monitor carefully,'' Frieden told NBC's Today show from CDC headquarters in Atlanta.
Health officials and lawmakers have been prepared for the possibility that a patient would arrive on U.S. shores undetected. Frieden briefed President Barack Obama on the Ebola issue on Tuesday and they discussed isolation protocols.
"People can be confident here in this country that we have the medical infrastructure in place to prevent the broad spread of Ebola,'' White House spokesman Josh Earnest told CNN on Wednesday. "The CDC and the local health officials in north Texas are taking the responsible steps to ensure the safety of the broader public.''
President Obama has called Ebola a national security priority for the United States and has called on the rest of the world to also regard it as a threat.
The Pentagon said Tuesday it is sending 700 U.S. soldiers to Liberia to help that country handle the outbreak. Seven hundred Army engineers also will help build treatment centers. No U.S. military personnel will provide direct care to Ebola patients.
Widespread US outbreak unlikely
Some other health experts have said, given the information from the CDC so far, a widespread outbreak in the United States appears unlikely from this one case.
"While it's not impossible to transmit it, it's not going to breakout and transmit [to] a whole neighborhood or a whole city,'' Dr. Ezekiel Emanuel, a former White House health adviser, told MSNBC.
Elsewhere in West Africa, the CDC said Tuesday it looks like the Ebola outbreak in Nigeria has been contained. Officials said there have been no new cases since August 31, and the 21-day monitoring period of those who came in contact with those infected ends Thursday. There were 19 conformed Ebola cases in Nigeria.
The CDC also says Senegal avoided an Ebola epidemic when authorities there isolated that country's only Ebola case in August.
Twelve other people in the U.S. have been tested for Ebola since July 27. The CDC said all those tests came back negative.
Some material for this report came from Reuters