[Lewis Thomson (OP)]

Donald would like to know the answer to this question.

"Zoonotic diseases are pathogens that usually infect nonhuman animals and opportunistically infect humans, where the human host is often a dead end.  Are there pathogens that travel from humans into nonhuman animals? Reports of zoo animals getting COVID 19 are examples?"

Discuss your findings in the comments below...

[alancalverd]

Guinea pigs are very susceptible to a number of common human infections - hence their use in medical research.

[Shraddha]

Certain viruses with similar receptor binding proteins (RBP) can pass on from animals to humans or vice verse through natural selection process.

[Bored chemist]

Well...
"recent research establishes a connection and attributes the spread of the disease to its transmission through international trade routes into native ecosystems.[5]"
from
https://en.wikipedia.org/wiki/Chytridiomycosis
It lookslike our actions spread diseases we are not directly affected by

[evan_au]

Chytridiomycosis

I heard that the Chytrid fungus that is killing frogs around the world was spread by human pregnancy tests.
- The early pregnancy test used from the 1930s to the 1950s used the African clawed frog, Xenopus (before we got RAT tests for pregnancy)
- Urine from a pregnant human induced these frogs to lay eggs
- These frogs were exported from their native Africa around the world
- Xenopus frogs are unaffected by the Chytrid fungus
- But this export industry spread Chytrid fungus around the world, and is now killing many species of frog which have no immunity to it...
https://en.wikipedia.org/wiki/Xenopus#Model_organism_for_biological_research
https://pubmed.ncbi.nlm.nih.gov/25843959/

[Bored chemist]

I heard that the Chytrid fungus that is killing frogs around the world was spread by human pregnancy tests.

There was also a suggestion that it was transported on/ by the scientists looking into the spread of the fungus.
I don't know if that was true, but it's clear that mankind spreads bugs.
https://en.wikipedia.org/wiki/2001_United_Kingdom_foot-and-mouth_outbreak
Foot and mouth didn't swim across the channel.