What could have prevented the Cholera outbreak in Haiti?

Not having an earthquake wreck the already fragile fresh water and sanitation infrastructure, or having a robust public health organization in place to combat or forestall it afterward. Even New Orleans had a high risk of cholera after Katrina.

Rebuilding housing with plumbing for all those still living without it.

A widespread vaccination campaign.

Clean water.
Perhaps not ever cutting ties with… France? It was France, right?

Clean water, adequate plumbing, health care, an effective government.

Their country was destroyed in the earthquake, homes were destroyed, what infra-structure there was, was destroyed. They did not receive enough help. They needed help to shelter the people who were left alive, but no country was willing to take the extra step to actually put up shelters for these people. So, with no shelter & no safe drinking water & no plumbing – they were sitting ducks when the rains came & turned their lives into a sea of mud & misery. It the US had not been embroiled in having invaded Iraq, we could have used the money to actually help these people. However, this would have meant that the military/industrial complex would not have made the money they have made off of the Iraq invasion. So, the simple answer is the cholera outbreak could have been prevented if we had helped them, but there was no money in it – so we didn’t.

Like @CyanoticWasp said. Prevent the earthquake so the water does not become contaminated.
Let me know when you figure out how to prevent an earthquake.