Before the Second Coming of Christ, an overflowing or desolating scourge—a desolating sickness—will be poured out from time to time upon the earth. Shortly before the Babylonian captivity of Jerusalem, Isaiah prophesied to scornful men who ruled the once holy city (see Isaiah 28:14):
Because ye have said, We have made a covenant with death, and with hell are we at agreement; when the overflowing scourge shall pass through, it shall not come unto us . . . [but] your covenant with death shall be disannulled, and your agreement with hell shall not stand; when the overflowing scourge shall pass through, then ye shall be trodden down by it. (Isaiah 28:15, 18.)
When mortals boast that they can escape death of themselves, God is obliged to disabuse them of the notion. On several occasions, such as in 588 B.C. and 70 A.D, He has flattened Jerusalem when the people of that city rejected and killed the prophets including, ultimately, the Son of God.
A scourge, according to Merriam-Webster, is "a cause of wide or great affliction," but it appears from latter-day scripture that this scourge is more than an affliction: it will lead to the death of many souls "until the earth is empty":
For a desolating scourge shall go forth among the inhabitants of the earth, and shall continue to be poured out from time to time, if they repent not, until the earth is empty, and the inhabitants thereof are consumed away and utterly destroyed by the brightness of my coming. (D&C 5:19.)
Later in modern scripture we read:
And there shall be men standing in that generation, that shall not pass until they shall see an overflowing scourge; for a desolating sickness shall cover the land. (D&C 45:31.)Here the Lord tells us that the scourge will be a desolating sickness that will cover the land. It is easy to imagine, given recent news, that a disease or series of diseases could get out of control and take thousands even millions of lives, in spite of the frantic efforts of modern medicine.
The knowledge and wisdom of men cannot save us from the decrees of God which will remain in force unless the inhabitants of the earth repent. Given what we know, that repentance is not likely. But one can hope.