It was in September that the disease struck and completely knocked out the World Cup winner, 32-year-old Röiseland.
It was not possible to exercise and the weeks and months just rolled by.
- It was tough, maybe the hardest thing I've been through in my biathlon career.
I was completely knocked out by the virus infection and have had to fight hard to get my body working again, says Röiseland from the firing range in Pokljuka.
Never getting well and feeling tired from the slightest effort made for a difficult everyday life.
- Having to live with that uncertainty about when I can come back has been tough to go through.
That makes me extra happy to do my first race this season.
There are no performance targets.
The important thing is how she feels after a maximum effort.
She has run a single test race before the season debut.
Important how the body works after the race
- I have no goals, I just want my body to work.
I will probably be a bit rusty after not having raced and I won't have my best race of my career but I hope to get some positive responses both during and after the race, which is perhaps most important, that the body is able to recover , says Röiseland whose big problem is that the body has not been recognized, it has not responded as she was used to.
- It will be difficult to match the Swedish girls, but hopefully I can offer opposition in the WC.
I have a dream of once again being able to participate and fight at the top again, says Röiseland, who took a long time to think this spring if she would continue for one more season after all.
However, the other Norwegian ace, Tiril Eckhoff, is still missing due to health problems.