Patients are being urged to stay away from GPs amid fears of a “Monday morning meltdown” as a result of the global cyber attacks.It comes amid warnings that the crisis could spread to other sectors, with a wider “escalating threat” as millions of workers switch on their computers.The director of Europol raised fears that the cyber attack that has hit NHS services and global businesses “will continue to grow” as people return to work after the weekend. The head of Britain’s National Cyber Security Centre echoed the warning, raising concerns that many existing infections may yet to have been detected, and others could spread within networks.He said the crisis could develop “at a significant scale” in coming days.The leader of Britain’s family doctors urged patients without appointments to stay away from GP practices at the start of the week unless their need is urgent.Dr Helen Stokes-Lampard, chairman of the Royal College of GPs, said the attacks, combined with precautionary measures, have had an “extensive impact” on GP practices, some of which are likely to struggle on Monday.Last night, she said: “The concern is that on Monday morning the appointment system may not be working, some places may not be able to access routine results, even the phone lines in some cases may not be working.”“If it is routine we are saying please leave it a day or two – if you are urgent we will prioritise but if not please give us a couple of days,” she said. On Sunday he said: “It’s very likely tomorrow that there will be some new cases emerging, possibly at a significant scale, but we don’t know.”So far, the scale of the damage has been limited by a UK security researcher, hailed as an “accidental hero” after registering a domain name to track the spread of the virus, which ended up halting it.The man is today revealed as Marcus Hutchins, from Ilfracombe in Devon.The 22-year old warned that a further attack is likely, saying hackers could upgrade their virus to remove his “kill switch” rendering any systems which are not patched to be vulnerable. My real life friends don’t know about my blog/twitter/job, etc… So today is going to be interesting.— MalwareTech (@MalwareTechBlog) May 14, 2017 Darien Huss, 28, who worked with the British 22-year-old to stop the cyber attack Urging patients to stay away unless their need was urgent, she said: “We are saying to the public, please bear with us. “The system may be compromised, but if you are urgent we will prioritise; if it is routine we are saying please leave it a day or two.”If phone lines were not working, patients in need of urgent appointments should make their way to surgeries to seek them out she said.However, the leading GP said the situation across the country was unknown, with no central data held on which operating systems were run by surgeries, or the extent of the impact.Many practices would have tried to carry out security updates over the weekend, she said.But there remain fears that the true damage could become clear as thousands of doctors try to log on.“In some cases computer systems will have been patched over the weekend but what we are frightened about is everyone logging on and there being a massive drain on the system as every computer is updated,” she said.Health officials have urged the public to use the NHS wisely, and said anyone with an appointment at a hospital or GP surgery should attend unless given specifically told not to.At least 47 NHS organisations have been affected by the crisis, with thousands of operations, tests and appointments disrupted as screens went blank across the country. The impact on GP services has been less clear, with the cyber attack occuring on Friday afternoon as many surgeries prepared to close for the weekend.Health officials are concerned about how the systems will cope when 8,000 GP surgeries open this morning, with no central record of how many surgeries have been affected.Since Friday’s breach more than 200,000 victims – including the NHS – across 150 countries have been infected by the Wanna Decryptor ransomware, also known as WannaCry.Europol director Rob Wainwright said he had been concerned for some time that the health service was not properly protected, unlike banks who had put “a proper strategy in place”.And he said he was fearful that the virus could spread across other sectors, with particular risks today as most workers return to their desks.”At the moment we are in the face of an escalating threat, the numbers are going up, I am worried about how the numbers will continue to grow when people go to work and turn their machines on Monday morning,” he said.Mr Wainwright said: “What is happening here is the exploitation of a flaw in the Microsoft operating systems. It is only affecting those computers that are not patched. We have been concerned for some time that the healthcare sector in many countries is particularly vulnerable.” Ciaran Martin, chief executive of the National Cyber Security Centre (NCSC) said the situation could worsen as the week goes on.“The way these attacks work is that there are compromises of machines and networks that probably haven’t been detected, and also ones that have been detected can spread. “It’s very important that people patch their systems now,” he said.”We have stopped this one, but there will be another one coming and it will not be stoppable by us,” he said.”There’s a lot of money in this. There’s no reason for them to stop. It’s not really much effort for them to change the code and then start over.” On Sunday afternoon even hospitals – including Barts NHS trust, the largest in the country – were continuing to divert patients from Accident & Emergency departments, as they battled the crisis. The rest have been able to restore their functions, leaving them to attempt to sort out a major backlog of patients and attempt to identify what information has been lost since systems were last backed up. Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings.