Flood spore

"One single Flood spore can destroy a species."

- Rtas Vadum

Flood Spores are the most basic of Flood forms that are crucial in the formation of Flood hives. Spores are also used as methods of suffocating future hosts and clearing the area of uninfected hostiles. It has not been specified if there is only one type of spore or if there are others, though it is known that the Infection Forms utilize encapsulated Flood cells referred to as "spores" when infecting other life forms.

The spores that have been witnessed the most frequently are a variety that will stay airborn, and will perform functions such as clogging air filtration systems, allowing for more efficient access to host organisms. If a spore lands in an area that can support it, it will form Flood Growth Pods. If the area does not have enough biomass to support a Flood Growth Pod, the spore will spread over floors and walls until it covers as much as it can.

Under certain conditions, it is possible for a compatible host organism to be infected by Flood spores, especially if it is an active state rather than the normal passive one. The spores will enter the body and go about interfacing with the host's biology, consuming the victim's biomass and replacing it with Flood biomass, leading to biological detoriation and transformation. How an organism infected by Flood spores differs from that of a life form taken by an Infection Form is not clear, but in the few instances of this having been witnessed, the infected organism retains a greater percentage of its biological make up than a Combat or Carrier Form does.

Trivia

 * You can see Flood spores in Halo 2 and Halo 3 on levels where there is extensive Flood infection, such as the Quarantine Zone and Cortana.
 * The Special Operations Elite Kusovai was horribly infected when he inhaled too many Flood spores. Due to the fact that he had been infected in this secondary manner, his rate of mutation was far slower than that done by an Infection Form, and he was not physiologically distorted in the same manner as those originating from the primary means of Flood infection are. These consequences of infection via Flood spores is next witnessed when the Prophet of Truth is infected by the Flood.
 * In Halo Wars, there is a configuration of the Flood Spores that are referred to as "spore clouds", and they only appear after a Flood Growth Pod has been destroyed, or a Flood Launcher fires flood biomass at opposing forces. Infantry that have been attacked by these spore clouds will be transformed into Flood Combat Forms, which renders the Flood Launchers a formidable threat to attacking infantry. Whether or not this is an actual function of the spores or if it is simply an artifact of gameplay, such as the non-canonical presence of shields in Red Team's MJOLNIR armor, is unknown.
 * In halo 2 it is seen that when the gravemind speaks, Flood spores emit from his 'mouth'.