There were too few helicopters to pluck all the survivors from the flood. There were even fewer to deliver food to the growing informal camps on high ground. People are not starving yet, but food is becoming as much a matter of urgency as rescue. It is not just a case of preventing malnutrition. Bodies weakened by hunger and the lack of clean water provide a good refuge for disease, particularly in overcrowded camps.
Aid workers live in fear of the first cases of cholera.
Not all the tree dwellers are grateful to see the helicopters. Some people furiously wave them away. Perhaps they fear to be tossed from the tree. It is more likely that they do not want to abandon what little they have left. From the branches, many people can see their homes.