With the disease Duplicants need more breathable gas than normal breathing in highly breathable atmosphere provides so they have to wheeze every so often. The problem gets worse if the atmosphere is less that "highly breathable". They will cough sometimes, which might interrupt jobs or sleep and will cause the release of 1000 Slimelung germs into the environment.
To treat Slimelung, the Duplicant should be in a medical bed in a well ventilated room from which the germs can not spread further. It does not affect treatment if the germs are breathed in during treatment but the Duplicant can get quickly reinfected if there are still germs presents when he has been healed. Duplicants who perform medical aid to the Duplicants on the medical bed can get infected if the atmosphere is too contaminated.