Locusts, wars, droughts, and disease, they are all scourges. This is not God’s way of educating human beings; it is, rather, the result of our moving away from Him. Scourges happen when we stray from God. His wrath then comes to make us remember Him and ask for His help. It’s not that He arranges and orders, so to speak, these calamities. Rather, God allows them to happen because he sees how far human evil can go, and how unwilling we are to change our ways. This is His way of bringing us to our senses. But it is not something that He has arranged; rather, it is the natural result of our own self-will, our own actions.
God told Joshua  not to exterminate the tribe of the Philistines, because the Philistines were supposed to be a scourge to the Hebrews every time they would forget God. So every time the Hebrews abandoned God, the devil acquired rights over them, and he would have his “cousins,” the Philistines, attack them. They would take the Hebrew children, smash them on rocks and kill them. Once when the Hebrews were attacked without being at fault, God fought on their side. He sent big hail, the size of stones, and destroyed the Philistines, because in that case the Israelites had a right to divine intervention. 
Think about the many promises God made to the Hebrews about the Temple of Solomon and the many times that it was burned and ravaged. When the people of Israel would stray from God, the prophets would weep and cry out for repentance, but the Israelites would shut their ears. They thought complacently: “Since God blessed the Temple when Solomon built it, and said that from now on our people will be blessed and holy, everything, our walls and our Temple, will stay in place as He promised.” 
Well, God did make this promise, but only on the condition that the Hebrews live righteously, His Grace was indeed upon the Temple, but when they broke the commandments, He allowed for it to be burned and destroyed. Only after they repented were they able to rebuild it.
For example, during the reign of King Zedekiah, when the people again strayed from God, Nebuchadnezzar came along and set the Temple on fire. He destroyed the city walls, took many of their leaders prisoner, and took them in chains to Babylon.  Of course, together with those that were at fault, there were also many that were innocent. These latter reaped a heavenly rewards for their innocent suffering, while the guilty paid for their sins…
The faithful who obey the commandments of God receive His Grace. God is, shall we say, obliged to help them during the difficult years in which we live. I have heard that a new disease  has appeared in the United States. Many people who live unnatural, sinful lives are infected by it and die. I’ve been told that now the disease has also appeared here. You see, it’s not God that destroys people. It is people that destroy themselves and their kindred. In other words, it is not that God punishes them, but that they impose their own punishment by the sinful lives they lead. And it is not hard to see that people who perish are those whose lives have lost all meaning.
– Geronda,  why haven’t we found a cure for cancer yet? Is it that God does not allow it, or that we don’t ask for his help?
Well, the bad news is that even if a cure were to be found today, another, new illness would appear. There was a time when it was tuberculosis. Then, they found a cure. Now, it is a new disease, cancer. And if God were to help cure cancer, another disease would appear. Human beings will once again be the cause, and it will go on this way, with no end in sight.
The above wisdom is from St. Paisios the Athonite. A couple of points I want to summarize from his teaching:
First, the calamities we see in this world are allowed by God, but they are not arranged by Him. They are a natural result of our sinfulness, which corrupts both mother nature and human nature. Through sin, death and suffering enters the world.
Secondly, I think it is worth noting that St. Paisios emphasizes that the righteous suffer together with the unrighteous. This may seem unfair, but that is because we lack an eternal perspective. If people suffer with humility and love in their hearts, lacking pity for themselves, but filled with compassion for their fellow human beings, then their suffering will bestow upon them a significant spiritual reward in this age and the one to come. If we struggle with this, it is because we truly lack faith in God and eternity. It is because we are so caught up in this world that we can’t even see the one to come. May God help us all to re-calibrate our focus on that which is permanent rather than the temporal.
All text, except my own reflection, is from With Pain and Love for Contemporary Man published by the Holy Monastery of Evangelist John the Theologian, Souroti, Thessaloniki, Greece. 2011. Bold text is my own emphasis.
 Cf. Josh 13:1-2; Jdg 3:1-4
 Cf. Josh 10, 11
 Cf. I Kg 9:1-9 (LXX: III Kg 9:1-9)
 Cf. II Kg 24-25 (LXX: IV Kg 24-25)
 This was said in November of 1984. The Elder is referring to AIDS.
 Geronda (pronounced “Yeronda”) is Greek for Elder.