Can toilet or sewage aerosol transfer eggs of human parasites? Flushing a toilet produces hundreds of thousands of tiny droplets containing viruses and bacteria (source). Additionally vomit and feces of infected people sometimes contain extremely high concentrations of viruses or bacteria. Similarly, sewage water produces droplets and was proposed as the transmission mode in the SARS outbreak in Hong Kong in 2003. * * * Apart from viruses and bacteria being transferred through toilet and sewage aerosol, can human parasite eggs be transferred as well given the droplet size? I'm interested in the aerosol, not the relatively large droplets that land on the toilet itself.

Common small protozoa that are present in infective loads in stool have not been documented in toilet aerosols. The size of the organism is going to be an issue here. As you can see from this table from the CDC, intestinal parasites (and ova) of concern to human health are larger than most droplets. Compare, E. coli and Shigella (0.5 - ~2 $\mu m$). Salmonella tends to be a litter larger (up to 5$\mu m$), but I expect those 5 $\mu m$ specimens are not the ones transmitted through aerosols. Cryptosporidium would probably be the most likely candidate, and that's one shown in the first linked study to _not_ be present in aerosols. I wouldn't say it's impossible, but certainly transmission through aerosolized particles is less likely than for the smaller viral and bacterial organisms.