Different pathogen entirely. I don't think there is any actual science behind this, though you're right that it was a widespread belief (as was "cats will suck the life out of a baby" and "you can't get pregnant if you're nursing" etc...). They have some similarity, but they're not the same. I hope you never do either. Sadly, that's not uncommon for immune compromised people. Chemo is gonna get you no matter what... Socks on the hands to prevent scratching was also popular. Big thick ones.