It's likely this man in Brazil came in contact with many people considering it was Carnaval time and that Sao Paulo is a huge densely populated city.
My understanding is that this virus is less contagious in humid conditions than in dry air. It will be interesting to see if the spread in Brazil where it is hot and humid now is lower than the spread in Italy where it is winter. Although it would appear that Brazil has identified patient zero while Italy did not. It all depends on how many people this Brazilian man came in contact with while he was contagious and before he sought treatment.
A lot depends on how many air conditioned spaces this particular Italian frequented.
While hot/humid (and for ‘hot’, think 90F) may lower the life span of the virus on surfaces, the temp/humidity of air conditioned spaces is just like it likes it.
Africa and South America likely already have the virus. They don’t have test kits. So don’t think that they are free of the virus. They are just free of modern health care. You will see them get the virus and have a million cases in a very short time. The virus is coming. Its even coming here. You can’t stop it. But if you can slow it down, you can manage it. Right now the Chinese are overwhelmed. Doctors and nurses are sick. They have few masks and little oxygen. So if you get it in China, you just have to take your chances. Plus the pollution and heavy smoking makes it more fatal than it would be in Europe or America.
If you slow it down you get two very large benefits. One, your health care system is more likely to be able to handle the strain of a small epidemic potentially saving the lives of many with severe cases. Secondly, it takes two years to produce a flu shot for this virus. One year to figure out the virus and test it. And one year to grow it enough to produce the numbers of flu shots capable of handling the well population.
I don't think we can depend on heat and humidity to kill something that lives quite well in a mostly water human body at 98.6°F, and even when that body runs a high fever...