Language miscommunication and culturally defined gender roles. So sometimes it could be hard for you to understand the way your partner phrases something or you don’t understand what they’re saying. Defined gender roles is just about how some cultures will treat women differently someone may have a view that women should be cooking and cleaning in the relationship and this puts a strain on everything.
That statment is true if that is what you are looking for
There were more but they weren't discovered as they were not viral and treatment was unknown and research were not done.