One of the things that Bill Gates mentions in his recent TED talk about the coronavirus is that we need to be aware of what might be coming in developing countries, particularly in the southern hemisphere with winter about to arrive. (There's some evidence of a relationship with temperature.)
So far, countries like Brazil have been criticized for taking a laid-back approach to fighting the coronavirus. But the same could be said for many, or perhaps most, countries around the world at the outset.
However, in the case of densely populated slums -- like Brazil’s favelas -- the problem is expected to be more severe. Without the ability to socially isolate and without proper services, it is questionable whether they will be able to "flatten the curve" in the same way that some developed countries have. There's also a lack of government oversight in these communities.
Incidentally, the Financial Times is reporting that organized crime has started to step in to fill this void -- and it is happening over WhatsApp. Here is an excerpt from the above article: “Whoever is caught on the street will learn how to respect the measure. We want the best for the population. If the government is unable to manage, organised crime resolves,” read one message sent to residents of a Rio de Janeiro slum.
One hope is that rich countries will be largely through their outbreaks by the summer and that a vaccine will be well on its way.
(On a related note, here is an excellent slide deck from the London Business School on the economics of this pandemic. It's very comprehensive and worth a read.)