Does investment in medical tech help minimize civilian loss when you have a water plague?

yes

ok thanks

It improves your chances to cure the plague faster. So to answer your question, it can.

Hate to let this guy know but for others that visit this forum medical gives you better chance to cure plague as celphi said, you could clear out a stack of 8-12 plagues in few turns.

but the biggest benefit to medical is the reduction of losses on attacks

civs/units/resources.