I loaded up my save game that I was playing earlier today, and approximately 10 million slimelung germs appeared in a cloud of CO2 in my base reducing my duplicants' immume system to zero in a matter of seconds. There were no germs when I saved and closed my map earlier. Loading an earlier autosave from about two cycles in advance had the same problem.
Steps to Reproduce
All I did was load my save game and the germs appeared out of seemingly nowhere.
This issue has not been confirmed by a developer yet.