[Ger-Poland-Volhynia] Plagues? Foreign armies?

[F&RM Haddad]

I'm learning the importance of knowing some of the history of the areas we
research. And since I don't know this particular relevant history, I'm
hoping someone else does.

1) were there plagues in the - say - Gostynin, Warszawa, Poland area around
1825-1850? There seem to be a lot of deaths at that time among the people I
am researching. I know that in the early 1900's there was a plague in the
Kremianke area in Volhynia, for my grandfather and several of his siblings
died of it. I was told it was "Typhus" - the black plague revisited?
Speaking of which, the black plague was still decimating communities in
Wuerttemberg, Germany around 1635. Is there somewhere we can find out what
plagues were affecting what areas when?

2) And were there "maurading armies" going through the area from about 1800?
Reason I ask is that I've come across several births where the father is
unknown, and all around the same time period. One must consider the
possibility of rape by foreign armies on their way through. Other
possibilities exist, of course. But it seems to be a high proportion
relative to time periods before and after.

Rose-Marie