Slimelung germs can be found growing in Polluted Oxygen or Slime. They multiply quickly in these sources, as well as Polluted Water. This disease can be killed quickly by using Chlorine or can be removed from slime using an Ore Scrubber.
When inhaled, Slimelung germs build up over time and reduce the duplicant's immune system. Once this reaches zero, the duplicant contracts the disease Slimelung. This disease is fatal in 8 cycles if untreated, but each treatment resets this timer.
While inflicted, Duplicants need more breathable gas than normal and can suffocate in low-oxygen areas. They will cough sometimes and often need to recover breath, which will interrupt any activity (including receiving treatment). Coughing releases 1000 Slimelung germs into the environment, but these are mostly harmless in such small quantities, provided the room is not full of polluted oxygen.