Actually... The infection forms are only required to infect a human host if A) the host is still living and/or B) there is no considerable mass of Flood matter (I call it fungus) in the vicinity to envelop and infect the dead human. Other sentient as well as nnon-sentient races, may be infected by spores. Infection by spores, however, again, requires the presence of fungus growth to produce the spores. Forerunner, and Pheru, for example, may be infected by spores, while humans, are much more difficult to infect in that manner and most are immune... unless they ingest the spores, or are bitten/scratched by a spore-infected host, as that causes the flood-matter to enter theblood streem directly. All that aside... there are tendrils trailing off of those guys... just like the Prophet of Truth, they may have been directly infected by the hivemind/gravemind. ...But I read Waaaaay to far into things Sorry for my little rant.