Alan Gosling, 79, was identified on Thursday at the man who had become infected with a particular strain of avian flu.
The father-of-three, from Buckfastleigh, Devon, is believed to have caught the disease from ducks he had adopted.
He began to see some of his flock falling ill late last month, which resulted in all 160 being culled soon after.
Doctors then did tests to see if Alan himself had become infected despite the fact the H5N1 strain had never infected a human before – and came back positive.
The retired train driver is now stuck inside his home alone as he grieves his ducks, with his family growing increasingly concerned.
Mr Gosling said he was feeling "absolutely fine, but very lonely".
He said: "As far as health is concerned, I'm fine, but I can't stop thinking about the ducks.
"I'm as fit and healthy now as I was donkeys years ago, because looking after the ducks kept me busy and active every day.
"By now, I would be back out with them, except I don't have any because they killed them all.
"I can't believe it – some of them I had for 12, 13 years since they were tiny chicks and I hand-reared them.
"They all had different stories – and then I had to watch them being killed and I couldn't do anything to help them.
"At the moment, I don't know what to do with my days.”
Mr Gosling added: "One of my other hobbies that I will try to get back into is restoring old clocks, but at the moment I can't focus on anything else because my ducks are all I can think about.
"I keep turning it over in my head and when I go to sleep it's what I dream about. It never leaves my mind.
"Maybe one day I'd like some more ducks, or other birds, but it'll never replace what I lost.”
Daughter-in-law Ellesha Gosling, 26, and son Richard Gosling, 47, say they are worried about their relative.
Ms Gosling said: "The past couple of weeks have been hell. Alan told us when the birds were killed, it was the 'worst moment of his life'.
"The culling of his beloved ducks has destroyed him, it's broken him. It has been so stressful and an absolute nightmare for us as a family.
"Both myself and my husband have had to take time off work to handle it.
"He has asked questions about his health and we can't answer any questions because we don't know any answers.
"He has told us he is not poorly, but he's really stubborn and we don't think he would tell us if he was. We are very worried.”
Ms Gosling said her father-in-law was ordered to test for the disease after the flock of 160 ducks came up positive and were culled.
A press release shared by the UK Health and Security Agency (HSA) on Thursday confirmed a case in the South West of England, although it did not name Mr Gosling.
The statement read: "Bird-to-human transmission of avian flu is very rare and has previously only occurred a small number of times in the UK.
"The person acquired the infection from very close, regular contact with a large number of infected birds, which they kept in and around their home over a prolonged period of time.
"The risk to the wider public from avian flu continues to be very low. However, people should not touch sick or dead birds.”
The national outbreak of avian flu has led to other parks closing their duck ponds and enclosures in a bid to save their animals from the same fate as Alan's.
St James's Park, a royal park in central London, has taken precautionary steps.