Uvaldo Pino was a neighbourhood barber in Cerro, one of the poorer and more overcrowded districts of Cuba's capital, Havana.
In late December, the 46-year-old fell sick with vomiting and diarrhoea and died in hospital on 6 January.
The barber's family say he had two separate tests and both came back positive - for cholera.
"We don't know how he was infected," his sister, Yanisey Pino, told the BBC at the family's home, a few blocks from the capital's Revolution Square.
"He was treated, he had all the medicine, but his organs didn't respond. It was too late."
Yanisey added that her brother was a heavy drinker and had checked himself out of hospital the first time he was admitted.
A week after Uvaldo's death, Cuba's health ministry has not yet made any public pronouncement. But there are increasing signs that the barber's case is not an isolated one.
'Dozens' of admissions
Doctors are now making door-to-door enquiries in Havana and anyone displaying possible cholera symptoms is being tested. Suspected cases are being sent to the Tropical Medicine Institute, the IPK.
"All our wards are dealing with this issue - they are almost full," an IPK employee told the BBC by telephone, before saying she was not authorised to comment further.
Another staff member, contacted later and also not authorised to speak to the media, said the IPK did not have any confirmed cases of cholera at this point.
But Yanisey Pino says her brother was diagnosed with cholera both by his local hospital and the IPK.
The day Uvaldo died, health workers visited the family where they live - in several cramped houses around a small yard. Relatives and neighbours were issued antibiotics as a precaution.
The area has been disinfected and water samples were taken for testing. Meanwhile, nearby bars and cafeterias have been closed or instructed not to sell food or drink that is not pre-packed.
Elsewhere in the neighbourhood, there are similar scenes.
One resident, Yudermis, fell sick just before the New Year, along with four other relatives including her seven-year-old son. The family assumed they had food poisoning but Yudermis says her cousin then tested positive for cholera at their local clinic.
"The health workers then came here asking questions, like if we had diarrhoea," she explains inside their rundown family home as her son, now fully recovered, plays nearby.
"They sent us all to hospital by ambulance and the tests came back positive.
"There were a lot of people at the IPK," Yudermis adds, describing dozens of admissions while she was being treated, and not all from her own district of Cerro.
"I was in a bad way. It was frightening. But we're fine now."