Groups taking trips to beauty spots and some non-essential workers are among those who have continued to flout Boris Johnson’s advice on physical distancing in the UK.

In London on Monday there was anger over crowded trains and tubes, with unions saying doctors and nurses were being put at risk by being jammed into public transport with non-essential workers.

Parks and beaches were significantly quieter than at the weekend and shopping centres almost deserted – but groups of people, including teenagers and families, were still out enjoying the spring sunshine.

Quick Guide What are coronavirus symptoms and should I go to a doctor? Show What is Covid-19? Covid-19 is caused by a member of the coronavirus family that has never been encountered before. Like other coronaviruses, it has come from animals. The World Health Organization (WHO) has declared it a pandemic. What are the symptoms this coronavirus causes? According to the WHO, the most common symptoms of Covid-19 are fever, tiredness and a dry cough. Some patients may also have a runny nose, sore throat, nasal congestion and aches and pains or diarrhoea. Some people report losing their sense of taste and/or smell. About 80% of people who get Covid-19 experience a mild case – about as serious as a regular cold – and recover without needing any special treatment. About one in six people, the WHO says, become seriously ill. The elderly and people with underlying medical problems like high blood pressure, heart problems or diabetes, or chronic respiratory conditions, are at a greater risk of serious illness from Covid-19. In the UK, the National health Service (NHS) has identified the specific symptoms to look for as experiencing either: a high temperature - you feel hot to touch on your chest or back

a new continuous cough - this means you’ve started coughing repeatedly As this is viral pneumonia, antibiotics are of no use. The antiviral drugs we have against flu will not work, and there is currently no vaccine. Recovery depends on the strength of the immune system. Should I go to the doctor if I have a cough? Medical advice varies around the world - with many countries imposing travel bans and lockdowns to try and prevent the spread of the virus. In many place people are being told to stay at home rather than visit a doctor of hospital in person. Check with your local authorities. In the UK, NHS advice is that anyone with symptoms should stay at home for at least 7 days. If you live with other people, they should stay at home for at least 14 days, to avoid spreading the infection outside the home.

The Welsh government took strong action, shutting caravan parks and campsites and ordering holidaymakers home, arguing that this was an important tactic to save lives.

Statistics, however, show that most people were following the prime minister’s advice. Transport use was down and more people than ever are working from home.

Despite pictures of packed tubes and trains on social media, peak London congestion was down by two-thirds on Monday morning compared with a typical rush hour, according to the satnav firm TomTom.

Passengers wait on the platform for a Central line tube train at Stratford, east London, on Monday. Photograph: Daniel Leal-Olivas/AFP via Getty Images

The transport app Citymapper revealed that London, Birmingham and Manchester registered significant drops in public transport use, down to 23%, 25% and 26% of normal patterns respectively.

Its statistics for London mirror those being studied in government, which the Guardian understands showed tube travel down 81% compared with a normal day, and bus travel down by 69%.

Britain was lagging behind some other countries in the extent of its physical distancing, however. Peak congestion in Milan has fallen by 90%.

With thousands of NHS and other key workers throughout London still needing to travel to work, as well as many businesses being advised but not forced to close, a reduced schedule on the tube network meant people being packed together.

Finn Brennan, a district organiser for the train drivers’ union Aslef, said London Underground staff were “furious” that tube trains were so busy on Monday. He added: “This is endangering the health of the vital workers who have to use the system. The government must act now to ensure only essential journeys are made.”

Away from London, city parks were quieter and people tended to space themselves out on benches, although some could not resist going out in small groups.

In Cambridge a couple were spotted taking a punt on the River Cam before the boats were packed away. Children were also seen playing together on the swings in a playground in the city.

The news that McDonald’s was closing its restaurants from 7pm on Monday led some people to jump into cars and head to the drive-throughs. Big queues were seen in Birmingham, Wirral, north-west England, Romford in Essex, and Sleaford in Lincolnshire. In Mansfield, Nottinghamshire, staff were forced to manage the queues.

People queue outside a McDonald’s drive-through in Hattersley, Manchester. Photograph: Anthony Devlin/Getty Images

Caravan parks and campsites in Wales were closed to visitors on Monday. People visiting Welsh caravan parks or campsites will be asked to return home unless there are exceptional reasons why they should stay.

All children’s play areas in Cardiff were closed. A spokesman said: “The risk of transmission from child to child on play equipment is thought to represent too great a risk to the public.”

Snowdonia’s national park authority announced the closure of its main car parks following “the busiest visitor weekend in living memory”.

The mountain rescue service in England and Wales called on people to stop heading to the hills and taking “unnecessary risks” after national parks were inundated.

At the weekend, teams helped search for a five-year-old child missing near waterfalls in south Wales, rescued climbers from Surrey who got into difficulty on Mount Snowdon, and recovered from Kinder Scout in the Peak District a man who had suffered a heart attack. Some rescues were hampered after car parks overflowed and vehicles blocked vital access routes.

Mike France, chief executive of Mountain Rescue England and Wales, said it had been a “crazy weekend”. He warned that walkers, cyclists and climbers getting into difficulty might face long waits to be rescued and urged them to stay at home because rescue teams – all made up of volunteers – were being depleted as members went into self-isolation.