Wow, poor red raspberries! It does not look like the lesions are on the stems of the leaves. (So it may not be anthracnose, but it my be raspberry leaf spots.) http://www.extension.umn.edu/distribution/horticulture/DG1152.html
Or does this look the same? I found this web site. http://plant-disease.ippc.orst.edu/disease.cfm?RecordID=959
But this site is in the Pacific Northwest area of the United States and you are in Belgium, so this might not be the same as what viruses we have here. All the sites I listed are University extensions for agriculture. Maybe search your local ones University extension.

WOW, is right! never have I ever seen anything like it. I hope you are able to put a label on it; and get it taken care of... I really do hope you can get this taken care of.

I think thats orange rust best cut off and put right into garbage bag to contain spores. There no control other than remove plants are plant parts. Look around your plants these spores had come from some place near by. But ways I had orange rust come from nurserys on plants. Only had one time so never buy anyhing from that nursery again. Check for orange rust plants weeds have orange rust tall ones 8 foot high is as high as I've seen this plant desease above ground.

Rust is an interesting disease. Sometimes it needs a 2nd kind of plant (an alternate host) to survive, sometimes it doesn't.

I wasn't able to locate that sort of info about raspberry rust.

Management involves several things; you're too late for some things this year.

Cultural management
1. destroy any affected refuse
2. cultivate in late fall or early spring to cover fallen leaves, old stubs and more from last year.
3. remove & burn (discard; don't compost)as soon after harvest as possible
4. strip leaves from primocanes before tying them up
and also

Chemical management: either bordeaux or lime-sulfur when the new buds have produced 3/4 inch new growth.

Not easy to manage.

Good luck.