Using a standard USB to USB cord. I would rather not infect my windows 8 machine. My question is more about whether windows 8 will have been sufficiently updated to protect against the virus, which was acquired more than a year ago.
No, you can't because you can't connect two computers via USB host ports over a standard USB cord - Type A Male to Male cords are meant for non standard USB HDD enclosures, since the standard insists you use a type B connector on the device side.
Even without a virus, you will damage stuff.
On the other hand, windows 8 uses microsoft defender as its default antivirus. There's a bootable version of it. Its a good way to work out if defender would catch what's on it.
Better yet, scan the drive, clean it up, do a file level recovery from linux first, then reinstall.
A standard USB cable will not suffice to transfer data between two computers (and would likely cause physical damage!). The physical cable you would need is described in this article, and can be purchased at most online electronics stores, such as New Egg, Tiger Direct, E-bay, etc: http://www.hardwaresecrets.com/article/Connecting-Two-PCs-Using-a-USB-USB-Cable/248
In regards to the risk of an infection spreading, there are a lot of factors that are could result in connecting the computers up a mistake or not, such as the nature of the virus (it might not even be compatible with Windows 8), whether or not your protection on WIn8 has a fix for the specific virus, etc. A general best practice is to simply not connect the devices until you are sure they are both clean from viruses and other malware.
My best recommendation would be to use a bootable security program, such as Kaspersky Rescue Disk (http://support.kaspersky.com/4162), or similar. I would also recommend installing (if able) other security products on the old XP machine one by one and seeing if they can detect and remove the virus(es). I ususally figure if I can get 6+ programs to say it's clean, I'm probably good, but that's just my measure point.
It depends on which antivirus you use, you have your firewall up and running. I suggest you should not rather format the hard drive, connect it to your Windows 8 PC in Slave mode instead of Master and scan it. Before formatting the HDD take backup of your files but not programs.
Coming back to your original question. Yes Windows 8 is well-protected enough(Read: Windows Defender) to handle a year-old virus but one virus generally brings many viruses (Dangerous newer ones).
UPDATE Google - Comod Rescue Disk (CRD)