To get DH1 back you just need to run IDEfix (or LoadIDE). Without it the area outside the first 4GB cannot be accessed and because of this DH1 appears to be unreadable. But the data is not lost, it's just not accessible.
To get DH0 back you need to run HDToolbox and create a new partition in the empty space before DH1. If you enter exactly the same values as your DH0 had before, you'll get all your files back.
But the most important issue is to get rid of the virus. This should be the first thing you do.
- switch off the Amiga.
- find a bootable floppy disk which you didn't use since you were infected.
- make sure that it has the write protect swich on
- boot from it and then check all other floppy disks one after the other. If you find a file called D in the C directory, delete it, delete the Mount command and overwrite the boot block by
install df0:. Note that a Workbench disk will not boot without the Mount command, so if you have a proper Mount command on your uninfected disk, copy it to the formerly infected disk.
- Do this for every disk which might be infected. Be careful not to boot from an infected disk and not to run a program from an infected disk. Once you run an infected program you can (and must) start all over from the beginning again (switch off the Amiga, ...)
Every disk without the write protect switch on which you inserted into the drive while the Amiga was infected is probably infected now, too.
Be sure to keep the write protect switch on on all floppy disks. Only switch it off for a short period if you really want to save data to the disk and immediately enable it again afterwards.
Regarding backup of the RDB, there are some programs on Aminet which can do it.
TSGUI can do it, too:
http://thomas-rapp.homepage.t-online.de/downloads/tsgui.lhaJust select a partiton on the harddrive, then choose "save RDB to file" from the menu.