The smallpox blankets incident occurred in 1763 and there are documents showing the commander of Fort Pitt ordering his soldiers to give the blankets to the Seneca people.

Sure. But this was literally centuries after the initial and most lethal waves of infection.

I know there was an increase in syphilis among the indigenous Hawaiians around when they started getting colonized.

Ironically enough, Syphilis was likely a New World disease brought back by Italian sailors in the 1490s.

The real crime here was the rampant unchecked sexual assaults that colonists perpetrated on native people. This wasn't biological warfare. It was a secondary consequence of military conquest.