The individual was asked to self-isolate, along with four members of staff with whom they had been in close contact. Two of those subsequently tested positive for Covid-19.
Two additional members of staff who had not had close contact with the previous cases then developed symptoms that Friday.
By Tuesday, six staff members at the Wind Street pub had reportedly tested positive.
That evening, another employee was admitted to hospital “with a condition believed to have been caused by Covid-19”, Wetherspoon said. He was reportedly asymptomatic prior to attending hospital.
And on Wednesday, an eighth employee who hadn’t worked in the pub for nearly a fortnight was found to have contracted the virus.
While additional restrictions have been imposed elsewhere in Wales - in Caerphilly and Rhondda Cynon Taf - infection rates in Swansea remain relatively low, with 13 new cases recorded on Friday.
“We understand that seven of the eight employees who tested positive experienced mild symptoms and we wish them well,” a statement from the pub chain said. “Our thoughts are with the employee in hospital and we wish them a swift and full recovery.”
All staff at the Swansea pub have been give additional health, safety and hygiene training, the statement said, adding that additional social distancing measures had been implemented in staff areas.
“We have been working with Public Health Wales and the Local Authority with these cases, and they have advised that there is a low risk to customers at the pub,” Wetherspoon’s statement said.
"While it is not possible to create an entirely risk-free environment, adherence to social distancing guidelines and rigorous implementation of hygiene standards minimises the risk,” it added.
It comes after Wales’ first minister accused Boris Johnson of leaving a “vacancy at the heart of the United Kingdom”.
Mark Drakeford urged the prime minister to provide the devolved nations with a "regular, reliable rhythm" of engagement, saying just one meeting per week “would be a start”.
He revealed he had spoken to Mr Johnson just once since May, while Scotland’s first minister Nicola Sturgeon said she couldn’t remember the last time she had spoken with the Westminster premier.
It came as Mr Johnson said the UK was “now seeing a second wave coming in”, which he called “inevitable”.
Using his strongest language to date on additional measures to curb the virus’s spread, he also stated his reluctance for another full lockdown - while suggesting fatigue with restrictions had contributed to the rise in cases.
Asked whether ministers were considering a short “firebreak” lockdown, Mr Johnson said: “We're watching it the whole time and as soon as we've got more to say, we'll be saying it”, adding: “If and when we have to go forward with other local or national measures or whatever, we will of course be explaining very clearly to everybody how we see it.”
“If [the 'rule of six’] isn't going to work then of course we are going to have to take further measures,” he told reporters during a visit to the Vaccines Manufacturing Innovation Centre construction site near Oxford.
“But be in no doubt that we will want to be explaining what we are doing, taking people with us as we go and what I don't want to do is go into a second national lockdown of the kind we had in March, April - I don't want to do that again.”