Revelation 16:2 So the first went and poured out his bowl upon the earth, and a foul and loathsome sore came upon the men who had the mark of the beast and those who worshiped his image.

This disease is selective in who is infected.
This verse says horrible and very painful sores break out on those with the mark.
Perhaps some element or chemical in the mark disagrees with the biology of people.
In other words, you need to take the mark to buy, sell, and survive, however, common side effects are loathsome sores.
Humanity as seen plagues, epidemics, and pandemics throughout the ages.
With it came our opportunity to attack viruses, bacteria, and disease with medical technology.
Many diseases have been virtually eradicated.
But many diseases have yet to be discovered.
Look at the current pandemic.
And I do not put it past people to create a disease as a biological weapon aimed at a specific target.
You may be a good person and not wish evil on anyone but there are others not like you that would seek power to destroy others.
Adolf Hitler comes to mind.
How could anyone in their right mind destroy other human beings by loading them like cattle and forcing them to live in deplorable conditions while planning the death of each one?
It did not end with the war to end all wars.
It still exist and will exist in the end times.
The reason sores break out on those in our scripture is sin.
Sin is a disease that mankind cannot cure with therapy or medicine.
Only the blood of Jesus overcomes sin.
Accept Him as savior.