GPs across Havering have been left without access to their medical records and clinical systems after worldwide IT outages.
A software update by cybersecurity firm Crowdstrike has caused global issues to Microsoft systems - affecting trains, shops, pharmacies, GP practices and some councils in London.
In Havering, a number of GPs have been impacted that the Recorder is aware of in areas such Collier Row and Hornchurch.
Lynwood Medical Centre, in Collier Row, issued a notice on its website this morning saying that their clinical system, EMIS web, is currently down.
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The notice said: "We regret to inform you that due to a significant worldwide outage, our clinical system, EMIS Web, is currently down.
"We understand that this interruption comes at a challenging time and may cause inconvenience.
"Please be assured that our team is working tirelessly to manage the situation and continue providing the best possible care under these difficult circumstances."
It added that residents should anticipate longer wait times on the phone, and should only contact them for urgent issues.
Those waiting on routine appointments and prescription requests were told to wait until the systems are back online.
Kings Park Surgery, in Harold Wood, also put out an alert for patients - saying that the practice has "no access to clinical systems".
The alert also said that eConsult will not be available during the outage "due to the potential clinical impact of a delay in care".
Hornchurch Healthcare issued a statement in response to the outages, informing patients that they are "unable to access any medical records while this is ongoing".
The statement said: "We are only able to provide immediate and necessary treatment until the issues are resolved.
"North East London ICB is working to find a resolution as soon as possible."
Other practices in Havering to issue statements on the ongoing IT outages include Billet Lane Medical Practice, in Hornchurch, and Western Road Medical Centre, in Romford - both saying that their computer systems are down.
These are the GPs in Havering that have issued statements or alerts on the issue.
NHS North East London, which oversees GP practices across the region, has issued a statement on its website.
It said: "We are aware of a global IT outage that is affecting some of our GP practices, hospital services and patient record systems.
"We are working with our health and care providers across north east London to understand the effect this is having and to try and minimise the impact this will have on patients wherever possible.
"Business continuity plans are being put in place. The NHS has long standing measures to manage the disruption, including using paper patient records and handwritten prescriptions, and the usual phone systems to contact your GP.
"Patients are advised to continue to attend their appointments as usual unless told otherwise.
"For urgent help, please contact NHS 111 online or by phone for advice, but patients should be advised call handlers may be busier than normal.
"There is currently no known impact on 999 or emergency services, so people should continue to use these services if their condition is life-threatening.
"For urgent repeat prescriptions patients are advised to contact their GP practice or visit their local pharmacy."
NHS England said the "majority of GP practices" in the country are experiencing disruption.
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NHS England said: "The NHS has long-standing measures in place to manage the disruption, including using paper patient records and handwritten prescriptions, and the usual phone systems to contact your GP.
"There is currently no known impact on 999 or emergency services, so people should use these services as they usually would.
"Patients should attend appointments unless told otherwise.
"Only contact your GP if it’s urgent, and otherwise please use 111 online or call 111."
Its not yet clear when these issues to GP systems will be resolved.
Microsoft has issued a statement saying the "underlying cause" has been fixed, but says "residual impact" is continuing to affect some services.
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