In 2014, when Sierra Leone was hit by the Ebola outbreak, three local software developers kept the country's infrastructure working by rewriting it to #FLOSS. They saved hundreds of thousands lives when companies like Google and IBM backed off, calling the project too risky.
And their own recollection of the events with some technical descriptions:
https://medium.com/idtlabs/how-open-source-software-helped-in-the-fight-against-ebola-788bb3ca2bf0