It spreads quickly and is highly contagious. It can be fatal for elders and kits, and it has claimed the lives of many cats. Cats usually catch it during leaf-fall and leaf-bare, and sometimes it develops into large-scale epidemics. Whitecough is the milder form, but if untreated, it can develop into the much more severe greencough. Diseases and conditions Chest infections Ĭhest infections may result in a prolonged cough Whitecough and greencough are the most common chest infections known to the Clan cats.