@Iskarioth
The mangaka gave us the divergence point from our timeline pretty clearly in the first chapters and it is pretty close of the current date( remember , this series happens in the 2nd half of the 21st century ) and it clearly takes place in our world . So, it is reasonable to assume that anything not specifically stated by the mangaka to have changed is still the same. So, until the mangaka states otherwise, we have to assume that the rest of the world is still there, that there is still a UN, Geneva convention and international treaties. Sure, Japan might have gone North Korea ( like in Psycho-Pass ), but again, there is no indication of that so it would be illogical to assume that Japan just decided to go gung ho on the international communty just because.
On the ethics on informing the ill kid ... first, notice that it is not telling the toddler that I have a peeve with that, while I would definitely not aprove. It is not saying to the parents of the kid and to do so to avoid being forced to treat the kid ( and in treating, I mean not only cure,that apparently is not possible in this case, but to mitigate the disease, something that is hinted to be possible ). That is illegal as hell and legally is pretty much equal to involuntary homicide in terms of legal framing ... not mentioning the emotional costs on the parents :/
Second, and as someone that has a mild partly genetic disease ( not life threathning and able to be dealt with relatively small measures ), I was always told since early life that I had it and TBH I can't conceive that being kept in the dark would be advantageous in anyway neither to the kid me or to the the ones around me ( and if you permit me the frankness, I don't know anyone that has any kind of genetic disease that would prefer to not know they had it. They would very much prefer to not have it, but that is another kettle of tea ).