Brown, 31, lost six kilograms in weight because of the illness, but has now recovered to feature in Harlequins' trip to Exeter this weekend.
"I had an infection in my shoulder, and ended up with septicaemia in my blood," Brown told BBC Radio 5 live.
"I spent a few days in hospital, which wasn't the best, but it's all fine."
He added: "It's always worrying when you end up in hospital, but once I was in there and we knew what it was, I took the time to relax and get better."
Brown missed Quins' first two Premiership matches of the season, the victory over Bristol and defeat by Sale, while he recuperated.
"It's been a bit frustrating, because when you have an infection you have to take everything steady and see how you progress," he said.
I know if I want to achieve more things with England, and hopefully with the Lions, it starts by working hard with your club
"It's a bit like concussion; you have to see how your body reacts to exercise, keep lifting it each day.
"Luckily I've had no reactions. I've had the check-ups and blood tests, and it's all been fine so far."
Brown has played a leading role in England's success so far in 2016, starting each one of head coach Eddie Jones' nine matches in charge.
He says his focus is now on performing with Harlequins, at the start of a campaign which culminates in the British and Irish Lions tour to New Zealand next summer.
"Everybody would be lying if they said it wasn't in the back of their heads," added Brown, who has 52 international caps.
"I know if I want to achieve more things with England, and hopefully with the Lions, it starts by working hard with your club.
"Eddie wants us all to stand out as international players, which is too right - we should be.
"[With England] this is just the start. We know we haven't achieved anything at the moment.
"Achieving things is Grand Slams every year, beating southern hemisphere teams all the time - it's being number one in the world, and winning World Cups."
England full-back Mike Brown is in line to make his first appearance of the season after recovering from a virus which put him in hospital.