Likely spread by cucumber beetle. I have to use new potting mix and grow my cukes in a flower pot. Row covers and Kaolin Clay coating when flowering. Get the Gardens Alive Catalog - it has a section on pests and what to do - including of course what they want to sell you.
So, cucumber beetles destroying squash and melons but I get loads of cukes in pots? I’ve got Gardens Alive as an online bookmarked resource thru their blogs. I’ll go read up on those.