Jacobs was preparing to play his first game for the Power in the NAB Cup opener against Adelaide and Melbourne when he started to feel run down.
The promising 19-year-old had completed as much pre-season training as any draftee in the club's history and attributed his waning energy levels to "first-year fatigue".
It wasn't until a week later when he was unable to get out of bed that he realised something was seriously wrong.
"I'm asthmatic and I thought it was just the weather affecting my asthma, but then I had a really poor training session and by the weekend I just couldn't get out of bed," Jacobs told afl.com.au.
"On the Monday morning I thought I would train, but I had the worst headache I've ever had in my life and I couldn't. I had blood tests and the next day I found out I had glandular fever."
Jacobs returned to Melbourne to recuperate with the support of his family, but was only home a week before his condition deteriorated and he was admitted to hospital.
"I got a secondary throat infection and tonsillitis on top of that," he said.
"I went into hospital for five days and I couldn't eat, drink or talk. Two days after that I was just drinking through a drip.
"They were ugly times, but after I got out of hospital I was on the mend again."
Jacobs returned to Alberton late last month after a three-week absence.
The skilful defender was physically weak, having lost seven kilograms through the ordeal, and was restricted to walking laps of the oval while his teammates trained.
The first-round draft pick has since graduated to running, skills work and two weights sessions a day.
He has regained three kilos and said the recovery process had given him an opportunity to improve his strength.
"When I was drafted I was coming off exams where I was doing eight hours of study a day and wasn't as fit as I probably should've been coming into an AFL club," he said.
"My diet wasn't ideal because I was just eating food that would give me the energy to stay up.
"In the recovery group you do a bit more work in the gym and I'm leaner and stronger already. I lost a bit of that puppy fat and the weight I'm putting back on is muscle."
Jacobs is hoping to start full training in the coming fortnight and the best-case scenario has him playing with the Port Magpies by round three of the AFL season.
"The club's in no hurry to get me back out on the field and, as people keep telling me, hopefully I'll be playing in the business part of the season rather than at the start," he said.
"I'm aiming to be back by round three or four of the AFL season at best and then any time after that I can have a crack at getting into the Power side.
"I'm just taking it week by week. I know it's a cliché, but that's really what you've got to do when you're coming back from a sickness like this."
Ben Jacobs is a $100,500 midfielder/defender in the Toyota AFL Dream Team competition
