“Your holiday, our lives – turn around.” That’s the message painted on a square of chipboard in red, green and yellow outside a house in the coastal town of Newport, Pembrokeshire. Similar signs across rural Wales are less polite.

Locals in this tourist hotspot are incensed because second home owners and holidaymakers are travelling here to self-isolate in the countryside. Official advice is to avoid non-essential travel and the Welsh government has just ordered campsites, caravan parks and access to certain mountains to be closed.

But those with second homes, cottage holiday bookings and touring caravans are simply being urged to stay away.

The proportion of elderly here is higher than the national average. And NHS facilities are bare bones. There are seven intensive care beds in the nearest hospital, Withybush General, according to a 2016 document. Withybush is a half-hour drive away. The local health board says it is working with NHS Wales on increasing the number of beds and ventilators. But this is the main hospital in Pembrokeshire – and serves the county’s population of 125,000.

If those who become ill in Newport can’t be treated at Withybush, they will have to go to Glangwili General in Carmarthen, which is an hour’s drive and has 14 critical care beds.

It’s not just health fears that have locals worrying. Food shops were not prepared for an influx of visitors and supplies of staples such as flour, bread and lentils are becoming hard to find. Shop owners say the last few days have been as busy as the peak summer season.

Clare Thomas, shopkeeper and owner of Whole Foods of Newport, is quickly adapting to the crisis. The 43-year-old has multiple sclerosis and a teenage daughter and knows she must avoid getting the virus – but is keen to keep the shop open. She has noticed the town filling up over the last few days.

“A week last Friday, the first person I recognise from the summer came in,” she said. “He comes to us all the time, he’s got a second home here, he’s an accountant in London. He sort of said, ‘Oh London’s absolutely crazy, I’ve come down to escape.’ And I thought, ‘Oh my god, I know the virus is a bit more advanced up there.’ It didn’t feel very nice.

“Then Saturday, I just noticed more and more people coming in. By Monday, it was getting really busy, it seemed like summer here.”

She has made changes to the shop – customers now order from a table at the front and only two are allowed in at a time — but still she has been running out of stock. One of her two suppliers has stopped taking business and the other, Suma, has been able to deliver only half of her order. It isn’t just panic buying; she knows which customers are local and can see an influx.

The message in Newport, Pembrokeshire. Another on the right reads, ‘I agree with next door’ (Emily Clark)

“My daughter and I were coming out of Newport at the weekend and seeing all these big posh cars and we had a joke – first one to spot a local,” she said. “We went all through town and didn’t spot anybody. There was a Lamborghini, a Mercedes, big Land Rovers.”

Wanting to swap crowded streets and public transport for green space, fresh air and wide beaches is understandable. “I don’t blame them,” said Ms Thomas. “But I’m frightened of it and it is dangerous. We’ve got an ageing population, they’ll probably kill off half the people round here.”

There are nearly 4,000 second homes in Pembrokeshire, according to the council. The size of the average UK household is 2.4, so that could mean an extra 9,600 people for the county to take in.

Earlier in the crisis, businesses welcomed tourists. One holiday cottage company produced an advert that read: “SCHOOLS OUT! Escape to secluded Pembrokeshire with the family at non school holiday prices”. They have since withdrawn the advert and have stopped taking bookings.

Three counties in west Wales – Pembrokeshire, Ceredigion and Carmarthenshire – issued a joint statement on Sunday asking tourists not to visit. Welsh Assembly minister Vaughan Gething said he and the Welsh first minister are considering how to use legal powers to stop second home owners and tourists from travelling to the country.

The UK government updated its advice on Sunday, saying: “Essential travel does not include visits to second homes, camp sites, caravan parks or similar, whether for isolation purposes or holidays. People should remain in their primary residence. Not taking these steps puts additional pressure on communities and services that are already at risk.”

For some here, that advice is not enough. They say measures need to be strengthened.

Tim Thomas, an electrician who lives in Newport, said the Spar — the main store in the town — was stripped of food on Sunday night.

“I think it’s very selfish of them all, we haven’t got the infrastructure in this neck of the woods,” he said. “Jumping in the car and coming down to your second home is total stupidity.”

To anyone else thinking of travelling, he had a clear message: “Stay at home – Boris has made it quite simple. It’s very very simple.