Thomas Eric Duncan, the first person diagnosed with the deadly Ebola virus on US soil is faring worse and now in critical condition, health officials said Saturday, having previously described him as seriously ill.

“Mr. Duncan is in critical condition,” the Texas hospital treating him said. Duncan had traveled from Liberia to Texas in late September.

Thomas Eric Duncan, condition now critical

The update came as US authorities said none of the individuals believed to have had exposure to Duncan, including nine deemed to be at high risk, had shown any signs of Ebola infection.

“We are confident that none of those with definite contact had any symptoms related to Ebola, none of them had fever,” said Tom Frieden, the director of the US Centers for Disease Control and Prevention (CDC).

The nine people deemed at high risk would be monitored closely, Frieden said.

“We will be looking very closely particularly at the nine individuals in the coming days, understanding that the peak period after exposure is about eight to nine days but can be as long as 21 days,” he said.

Duncan 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, sparking concern over how many others may have been exposed.

Frieden said the publicity surrounding the Duncan case, and the mistaken decision to send him home from hospital, had heightened awareness amongst health workers.

“As we anticipated, the arrival of the first case diagnosed in the US has really increased attention on what health care workers need to do in this country to be alert and ensure that travel history is taken into account,” Frieden said.

The Ebola outbreak is the worst epidemic involving the disease on record and has spread into five west African countries since the start of the year, infecting more than 7,000 people and killing about half of them.

The virus, spread through infected bodily fluids, can only be transmitted when a patient is experiencing the symptoms — severe fever, vomiting, diarrhoea and, in some cases, massive internal haemorrhaging and external bleeding.