Networks were still unavailable today, nearly two days after a virus caused a "major incident" at Barts and The London NHS Trust.
Computer Weekly has learned that the virus caused a plethora of spurious messages to overload the trust's network.
The trust, which has installed the "Cerner" Care Records Service under the National Programme for IT [NPfIT], diverted ambulances to neighbouring hospitals for several hours while IT specialists shut down the networks and tried to find out how the virus penetrated them.
The virus was discovered on Monday afternoon. By this morning there was still only limited access to the trust's networks.
A spokesman for Barts said today that parts of the network are being brought up gradually. He said it was still not known how the virus got into the networks. It affected networks at the trust's three main hospitals: St Bartholomew's in the City, the Royal London in Whitechapel and the London Chest in Bethnal Green.
Barts has England's biggest centre for treating heart attacks, and also has specialist treatments for cancer. It is one of the capital's leading trauma and emergency care centres, and is home to London's air ambulance.
Ambulance services to the trust were diverted during the outbreak but early evening yesterday the trust began taking in ambulances again.
Hospital officials were telling the media, on the basis of their guidance notes, that the Care Records Service - part of the £12.7bn National Programme for IT - was working normally. They said the Care Records Service was unaffected by the virus.
But one official at Barts conceded that, with the network overloaded because of the virus, staff "might" have been unable to access the Care Records Service. He said that in that event staff would have reverted to accessing paper-based records.
Although this is a normal backup procedure it can cause backlogs of work and reduce the number of patients that staff and clinicians can see and treat.
The Care Records Service allows access to patient records. The hospital's networks also handled requests for X-rays.
In a statement yesterday the trust said, "The Trust's well rehearsed emergency procedures have been activated to ensure that key clinical systems continue while network access is being established.
"We have maintained a safe environment for our patients throughout the incident. Manual backup systems are in use and we are in the process of restoring the computer systems with priority being given to the most important areas for maintaining patients services.
"Operating theatres and outpatients departments have remained operational throughout the incident, though some non-essential activities have been scaled back. A&E remains open to walk-in patients and ambulances are being diverted to neighbouring hospitals in the short term."
Julian Nettel, chief executive at the trust, said yesterday, "This has been a difficult day, but by using back-up systems, manual procedures and working flexibly, we have continued to provide high quality care to our patients."
The trust says that medical staff have been able to make paper-based requests for laboratory tests and X-rays. Nettel said, "I would particularly like to thank all our staff, patients and other NHS colleagues for their hard work, help and support during this incident."
Read more on the IT Projects blog >>
Update: Parts of the Barts network were still down today (20 December 2008).