The 101-year-old, who served as a gunner in the Second World War, caught Covid-19 alongside his wife Ella, 92, back in March.
He was with his childhood sweetheart and companion for more than 70 years - but she died in hospital days after testing positive.
Wiping away his tears on camera, Mr Lister told his local TV station: "It's being lonely.
"Sometimes I'm in my room and the only time I see anyone is when they bring my meals."
The war veteran had also previously told the Eastern Daily Press that coronavirus is "worse than war".
And within hours of his story appearing on Anglia TV, people from all over the UK - as well as Canada, America and Australia - pledged to send Christmas greetings to his nursing home, Thorp House.
Hayley Attew wrote: "My children decorated a card today and sent it.
"I really hope he doesn't feel lonely with what will hopefully be an influx of well wishes and kindness sent to him by everyone.
"This story has made us think about things, so my family are going to write to a few care homes asking if they have anyone that would like to become our penpal/friend. No one should feel lonely."
Mr Lister was later filmed surrounded by letters from all over the country, as a care worker read his greetings aloud.
One card read: "Dearest John, we heard this year had been very difficult for you. So we wanted to send you a card to wish you a very merry Christmas.
Another read: "Dear John, you are an inspiration and a true gentleman."
When asked how the letters made him feel, Mr Lister said: "Elated. It opened my eyes."
Find out more about Thorp House