WHIPPS Cross University Hospital has been hit by a "crippling" computer virus, which has knocked out a large proportion of its IT system.
The fault, which first emerged last week, is still being cleared today by staff, but a Whipps spokeswoman said no patient care had been affected by the problem so far.
One hospital patient, who did not wish to be named, told the Guardian they had been informed that the virus had "crippled" scores of computers and created havoc for staff.
A spokeswoman for the hospital said: "Whipps Cross University Hospital NHS Trust can confirm that a number of its IT systems have been affected by a computer virus.
"At present, no patient care has been affected by this, and work is underway to ensure that the systems affected can be reinstated as a matter of urgency.
"The trust would like to reassure its patients and the local community it serves that it has a full business continuity plan in place for incidents such as this."
The hospital is expected to comment further and provide more information about the problem soon.
It comes after Barts and the London NHS Trust was criticised in an investigation in January over a virus which hit Bartholomew's Hospital, The Royal London in Whitechapel and The London Chest Hospital in Bethnal Green last November.
In that case a report concluded that the fault had the potential to affect the "wellbeing of patients and morale of staff, as well as the long-term reputation of the trust."
Some non-urgent operations were also postponed during the virus at the hospitals.
However the full circumstances behind the Whipps virus are yet to be established.