A repatriation flight carrying 32 Britons and Europeans from the coronavirus-infected cruise ship Diamond Princess landed in the UK on Saturday – amid growing fears for the welfare of some UK passengers left behind in Japan.

David and Sally Abel – who were on the cruise for their 50th wedding anniversary and who have been diagnosed with coronavirus – have contracted pneumonia, it was revealed. Abel has acute pneumonia while his wife has a mild case of it. “Dad is very weak,” said their son, Steve.

The Abels were among four Britons on the Diamond Princess who tested positive for coronavirus and were not included on the flight that touched down at the Ministry of Defence base Boscombe Down in Wiltshire shortly after 11.30am on Saturday.

The 32 passengers, who have already spent more than two weeks trapped on the ship off the coast of Japan, were then taken to Arrowe Park hospital, Wirral, for 14 days of quarantine. They have so far tested negative for Covid-19.

Arrowe Park had previously been used to quarantine 83 British nationals for 14 days earlier this month after they were flown out of Wuhan in China, which has been at the centre of the outbreak.

Infected passenger David Abel in his hospital room in Japan. Photograph: David Abel/PA

In the meantime the Abels’ children said their parents had been left in a hospital room in Japan that had no shower or bathing facilities, and had only been provided with basic paper towels. “They don’t know what’s happening, they haven’t had any treatments,” said their son, Steve. “They have been told that if they test negative twice they can go – but that doesn’t treat the pneumonia.”

The family, which has said it is willing to fly to Japan to bring the couple home, has criticised the Foreign Office response to their parents’ plight, saying it has been “next to useless”.

The NHS said it had started testing people for coronavirus in their own homes in London. This would be expanded to other areas in the coming weeks, said Professor Keith Willett, NHS strategic incident director for coronavirus. “Home-testing will be carried out by NHS staff, allowing people to stay home rather than having to travel, which is safer for you and your family and limits the spread of infection,” he said. “Anyone who is concerned they have signs and symptoms should continue to use NHS 111 as their first point of contact.”