WASHINGTON (AFP) - Liberian President Ellen Johnson Sirleaf said a man diagnosed with Ebola in Texas behaved irresponsibly when he travelled after being exposed to the virus, calling his actions "unpardonable".

Thomas Eric Duncan is the first person diagnosed with the deadly Ebola virus in the United States, after travelling from Liberia to Texas.

He was in contact with a known Ebola patient in Liberia, according to US media reports.

"The fact that he knew and he left the country is unpardonable," Sirleaf told Canada's public broadcaster CBC.

Sirleaf said although Liberia's airports are equipped with Ebola screening measures, Duncan slipped past authorities, which Sirleaf said could have put many at risk.

"(He) in a way put some Americans in a state of fear and put them at a state of risk, so I feel very saddened by that and very angry with him," she said.

The West African leader did not say what measures will be taken now, only that she would consult lawyers before deciding how to "deal with him" upon his return to Liberia.

Duncan is being treated in a Texas hospital and four of his family members have been ordered to stay home, as authorities continue to scour the community for people he may have come into contact with.

The deadly Ebola virus has so far killed 3,338 people out of 7,178 infected, most of them in Liberia, Sierra Leone and Guinea.

Duncan did not have a fever when he departed Liberia on September 19 but began to feel sick on September 24 after arriving in Texas.

He was initially sent home when he first sought medical care, leaving a four-day span when he was sick and contagious while in contact with others.

Once a patient begins to show symptoms like fever, vomiting and diarrhea, they can infect others who come in close contact with their bodily fluids.