What environmental factors contributed to the spanish flu and its spread?

I think this might help.

Avian influenza (bird flu) has the potential to cause a healthcare crisis of unprecedented global dimensions. Many predict a global pandemic far worse than the 1918 Spanish Flu, which killed 40 million to 50 million people. A larger, denser global population, coupled with modern transportation systems of both goods and people, could result in a pandemic killing far more people worldwide. The consequences of such a pandemic would stretch beyond just public health. International relations, commerce, politics, travel, medicine, and economic and social infrastructures would be affected due to widespread infection and worldwide mitigation efforts. 

1is using relevant evidence 2 is speaking

The american anti-slavery society (aass) (1833–1870) was an abolitionist society founded by william lloyd garrison, and arthur tappan. frederick douglass, an escaped slave, was a key leader of this society who often spoke at its meetings.