There are also more recent papers such as this 2018 paper concluding that rodent fleas could not have caused the second pandemic: https://www.ncbi.nlm.nih.gov/p

There are also more recent papers such as this 2018 paper concluding that rodent fleas could not have caused the second pandemic: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5819418/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5819418/