A number of operations have been postponed at Northwick Park and Central Middlesex hospitals following a nationwide cyber attack on NHS systems on Friday.

Patients are being urged to visit emergency departments for serious and life-threatening injuries only and use walk-in centres and pharmacies wherever possible.

Staff at the London North West Healthcare (LNWH) NHS Trust, are currently using paper-based systems after a virus attacked its IT systems but say no data has been lost.

Known as Wanna Decryptor or WannaCry, the virus that hit the NHS in England and Scotland, has infected 200,000 machines in 150 countries since Friday.

The virus was identified at 12.45pm on Friday afternoon in three PCs and two servers which serve Northwick Park, Central Middlesex and Ealing hospitals.

As a precaution they switched off “a number” of IT systems which have not yet been switched back on.

Fewer than 10 radiology appointments and elective operations due to take place today have been postponed.

Those needing to get in touch about appointments are asked to call the switchboard instead of sending emails.

Lee Martin, chief operating offier of LNWH, said: “Since Friday’s cyber attack, staff across the Trust have been working tirelessly to ensure patients are cared for safely.

“We identified the virus at 12.45pm on Friday in three PCs and two servers.

“As soon as the virus was identified we took immediate action to protect our systems from any data loss and further corruption.

“As a precaution we shut down a number of IT systems and some services are currently using paper-based systems.

It is the precautionary measures we have taken that have caused most disruption, not the virus itself.

“We continue to work with NHS Digital and will begin to switch our IT systems back on when we feel it is safe to do so.

“In the meantime we are asking the public to help our staff and visit our emergency departments for serious and life-threatening injuries and conditions only. Please consider the alternatives, such as visiting your local walk-in centre, pharmacy or calling 111 for minor injuries and advice. This will help relieve pressure on our services.

“We apologise for any delays and cancellations that patients will experience and we thank you for your continued patience and cooperation as we work to resolve these issues.”

The Trust has 9,000 PCs and 500 servers.