How do I remove a virus from a memory card?

Reformat the card.

Presumably you have a card reader, and presumably that card, when inserted, appears as another drive on your computer.

Reformat it. Remove any data you want to keep first, but then reformat it.

That will erase everything from the card. Data. Viruses. Spyware. Everything.

If for some reason you cannot reformat it on your computer, then once again, copy off the data you want to keep, and use your camera or other device to reformat it; most have this as an option.

We talk about "reformat and reinstall" as a last resort, or in some cases the only resort, to curing an infection on your system drive. The problem is that while this does eradicate the infection by erasing everything, it erased everything, including your operating system. You now have to reinstall, or perhaps recover from a backup image that was created prior to the infection.

With other drives we have a little bit more flexibility. It still really is "reformat and reinstall", but typically the "reinstall" part is significantly less of a problem. You can copy all the pictures off of your camera's SD card, and reformat it without much effort. Even other drives, such as external hard drives or internal hard disks, can be treated the same way, though in these cases the problem is often where to copy the data, and making sure you also don't copy the infection.

So that gets it off of your SD card.

But I'm still concerned.

Most viruses insert themselves into your system. Specifically, they copy files onto your system drive, and insert themselves in various system-related places like the registry. It's unclear how you've been clearing this off once you've determined you've become infected. In fact, it sounds like the tools you have at hand haven't been able to clean it from your SD card, so I don't see how your system isn't still infected as well.

It's quite possible, then, that even after formatting your SD card, your still-infected system might not put the infection right back.

Unfortunately I don't have a silver bullet for this situation. Not all anti-malware programs catch every possible malware. I would, in your shoes, run a variety of those tools, both anti-virus and anti-spyware, to attempt to clear off the infection.

If that still doesn't work, then you're faced with only one alternative.

Backup, reformat your system drive and reinstall everything.