Surely God could easily have prevented HIV from spreading. After all, the world did without HIV for a very long time. If God is looking after us, we should expect the level of suffering to stay constant or gradually reduce. It should never increase. Christians differ enormously about what is truly good.
Christians often say that suffering is caused by people doing evil.
However, unless God tells Christians what is truly good , in clear, unambiguous terms, then this defence fails. For people will often do evil when they think they are doing good, because God has not told them what is truly good. For example, some people may think it is acceptable to mutilate male baby children by cutting off part of their penis, because they think God has commanded them to do that. However, if God does not think removing foreskins is truly good, then they are inflicting suffering despite having purely good intentions, contrary to the Christian claim that suffering is caused by people having evil intentions. If God wants us to do what is truly good, then he should have chosen another medium other than the Bible.