The only known person to be suffering with Ebola in the United States is said to be in a critical condition in hospital.

The hospital has not provided any further details about Duncan’s condition, although they had previously said he was in a serious but stable condition.

It is understood Thomas Duncan had travelled from Liberia to Texas last month to marry his partner.

When Duncan came to a local hospital emergency room on September 25 he was sent home by staff who diagnosed his illness a low-grade fever. In the aftermath of this error the hospital claimed an error with the hospital’s electronic records system had meant the staff treating Duncan was unaware of his recent travel from Liberia. The hospital has since retracted this, admitting “there was no flaw” in the system and the team who saw Duncan had access to his travel history.

This lapse means Duncan was then in contact with several others while exhibiting symptoms of Ebola.

Health officials are now monitoring 50 people who may have had contact with Duncan. Nine are considered most at risk although none have so far shown any symptoms of the virus.

Elsewhere, the American freelance cameraman working for NBC in Liberia has tested positive for Ebola. He will return to the U.S. on Sunday for treatment.