Up to 100 people may have had direct or indirect contact with the first person diagnosed with Ebola in the United States, while four relatives of the man have been quarantined in a Dallas apartment.
Dallas County officials said 12 to 18 people had direct contact with the patient, Liberian national Thomas Eric Duncan, who flew to Texas from Liberia via Brussels and Washington two weeks ago.
The authorities said those people then in turn had contact with scores of other people. None of those thought to have had contact with Mr Duncan were showing signs of Ebola.
Mr Duncan was admitted to Texas Health Presbyterian Hospital on Sunday after hospital workers mistakenly sent him home days earlier.
The man needed an ambulance to return to the same hospital after being seen vomiting on the ground outside an apartment complex.
“His whole family was screaming,” resident Mesud Osmanovic said.
“He got outside and he was throwing up all over the place.”
Infectious disease experts said that time gap represented a critical missed opportunity that may have led others to be exposed to the virus.
Five Dallas-area students were among those under surveillance for the next 21 days, the time it can take for symptoms to appear.
Mr Duncan remains in a serious condition.
Quarantined relatives not showing any signs of fever
Department of State Health Services commissioner David Lakey said four relatives of Mr Duncan’s were under quarantine and did not have a fever and were healthy.
“There’s food being delivered to them … we’re arranging for that apartment to be cleaned,” Dr Lakey said.
Under quarantine is a woman, whom CNN identified only as “Louisa,” one of her children, who is 13, and two visiting nephews in their 20s.
Police and armed security guards were keeping people about 100 yards away from the apartment, with orange cones blocking the entrance and exit.
Maintenance workers using high-pressure water were scrubbing the parking lot with bleach.
Patient’s travel documents checked
Liberia’s information minister Lewis Brown expressed regret over one of its nationals carrying Ebola from Monrovia to the United States.
“Currently there are stringent screening measures in place at the Roberts International Airport which we believe are preventing the disease from spreading via air travel,” he said.
“We are led to believe that he posed no risks to other passengers or the crew with whom he travelled.”
The head of the Liberian airport authority, Binyah Kesselly, said Liberia could prosecute Mr Duncan for making a false declaration on his travel document.
Mr Kesselly said Mr Duncan was asked in a questionnaire if he had come in contact with any Ebola victim or was showing symptoms of the disease.
“To all of these questions, Mr Duncan answered ‘no’,” Mr Kesselly said.
Earlier, Mr Kesselly said the sick man knew that he had come into contact with someone who had eventually been diagnosed with Ebola, even though he left Liberia with no signs of symptoms.
The New York Times said Mr Duncan, in his mid-40s, helped take by car a pregnant woman suffering from Ebola to a hospital in Liberia, where she was turned away for lack of space. The woman died.
Infections continue in Ebola hotspots
Meanwhile, the Save The Children charity warned that five people were being infected with Ebola every hour in the West African hotspot of Sierra Leone and demand for beds was outstripping supply.
If the current rate of infection continued, 10 people every hour would be infected with the deadly virus there by the end of October, the London-based organisation warned.
The World Health Organisation put the death toll from the world’s worst ever Ebola outbreak as of last weekend at 3,338 people out of 7,178 cases in West Africa.
Reuters/AFP