According to the author of the book, the rider on the pale horse will destroy one-forth of the population of the world. His goal in the end time is to make war and a horrific war it will be. Killing as many as 1.75 billion people in a short span of time, it leads me to think that chemical gases and or plagues will be the cause. If in fact the pale horse uses chlorine gas, a huge segment of the population would be destroyed within minutes to hours. In Jesus’ parallel prophecy in Matthew 24, He explained that in the wake of religious deception, war and famine would come “pestilences” ( a contagious or infectious epidemic disease that is virulent and devastating; ) or disease epidemics
The first four seals of the book of Revelation The Expositor’s Bible Commentary (http://www.studylight.org/com/teb/ )says this about the color of the fourth horse: “‘Pale’ (chloros ) denotes a yellowish green, the light green of a plant, or the paleness of a sick person in contrast to a healthy appearance.” Put bluntly, this horse is the color of death .
Fourth Seal: Pale Horse Widespread Death on Earth – Revelation 6:7-8
7 When He opened the fourth seal, I heard the voice of the fourth living creature saying, “Come and see.”
8 So I looked and behold, a pale horse. And the name of him who sat on it was Death, and Hades followed with him. And power was given to them over a fourth of the earth, to kill with sword, with hunger, with death, and by the beasts of the earth.
The Pale Horse is more explicit in expressing death, hunger, and killing with the sword. Many suggest this is also about pandemics that are widespread disease that affects people in many different countries.
AIDS is only one that is considered to be pandemic. We are now seeing many new strains of viruses. Many concerns have been discussed and presented for the safeguard and protection against the dangers of the spread and effects of the bird flu for example, and/or in requiring mass population vaccination for the new strains of flu viruses.
In an age of medical knowledge and miracles, we have seen increases in all areas of autoimmune diseases that seem almost untreatable, or with only temporary relieve.