Bleach is king for disinfection. But you have to be careful using bleach as it can bleach the carpet (of course). For general cleaning 5% dilution of household bleach is generally recommended (so, 6.75 fl. oz. household bleach plus one gallon of water). But for the carpet, I wouldn't do it- or I would try starting with a lower (1% or 2%) concentration of household bleach.
Since bleach is kind of sketchy, benzalkonium chloride or n-Alkyl (40% C12, 50% C14, 10% C16) dimethyl benzyl ammonium chloride would be the next best thing. These antibiotics are the active ingredients from many lysol and clorox products (like wipes, 409, and hand sanitizers). I would recommend the same usage level (for these antimicrobials) for cleaning and disinfecting the carpet, as around the same levels that are used in wipes and 409 (that's 0.3%). In fact, I think that pouring 409 over the spot and then using a wet vac or steam cleaner to clean the spot would work perfectly well.
Now there are a ton of disinfecting carpet cleaners (antimicrobials require EPA registration) so, generally speaking, they are more likely to work. Some antimicrobial carpet cleaners might contain some form of benzyl ammonium chloride... whole others only contain alcohols (like phenophenol or phenoxyisopropanol)... and some contain both.
That being said, some companies like Bissel are able to sell 4.67% hydroxgen peroxide as a disinfecting carpet cleaner... if you poured that straight onto the carpet it should work, but I can't see how you could really dilute it and still expect it to work. So obviously, the EPA lets some stuff slide. I think that Bissel's banking on the fact that people rarely shop for disinfecting cleaners... and plenty of people opt for the good looking packaging. On that same note, I ran across a product called Microban... which contains: o-Phenylphenol 0.22% and Diisobutylphenoxyethoxy ethyl dimethyl benzyl ammonium chloride monohydrate 0.70%. Pretty good looking stuff, but the package is ugly as sin and the price is too high compared with say 409 (actually named CPPC EVEREST epa# 67619-10... Clorox tries to hide their products with names like Boris and Blondie), which contains 0.3% n-Alkyl (40% C12, 50% C14, 10% C16) dimethyl benzyl ammonium chloride.
For any product that claims to be antimicrobial, you can find the label here: USEPA Product Label Search.
Also be skeptical of instructions online for using all kinds of stuff- especially the one that pops up first on google which includes about 1/2 cornmeal. Using cornmeal isn't a good idea for disinfection. Borax... not really. Vinegar... a little. Vinegar with bleach... oh yes- but that could also go deadly wrong.