There were many violent outbreaks and even massacres of Jewish people during the plague because many thought they were to blame. Because the Jews were limited to ghettos and had strict rules of cleanliness like washing their hands before eating they were not hit as hard as other groups, and because of the high anti-semitism to begin with they became targets while no one really did anything to stop it the Jews found themselves to be scapegoats. Rumors flew of them poisoning wells and killings of Jews took place in Toulon, Barcelona, and more.

I’m not sure about Spanish flu conspiracies such as this but the term Spanish flu became popularized because there were censorships on reporting the lethality of the illness with WW1 participants to keep morale high but neutral Spain did not so reporters reported what they could and due to this it was perceived that Spain was dealing with the worst of it.

Porras-Gallo M, Davis RA, eds. (2014). "The Spanish Influenza Pandemic of 1918–1919: Perspectives from the Iberian Peninsula and the Americas

Anna Foa (2000). The Jews of Europe After the Black Death