Naming diseases was not always so complicated. Syphilis, for example, is drawn from a 1530 poem in which a shepherd, Syphilus, is cursed by the god Apollo. But the compound microscope, invented around 1600, opened up a hidden world of microbes, allowing scientists to start naming them after their shapes, said Richard Barnett, a historian of science in Britain.
Still, racism and imperialism infiltrated disease names. In the 1800s, as cholera spread from the Indian subcontinent to Europe, British newspapers began calling it “Indian cholera,” depicting the disease as a figure in a turban and robes.
“Naming can very often reflect and extend a stigma,” Dr. Barnett said.
In 2015, the W.H.O. issued best practices for naming diseases: avoiding geographic locations or people’s names, species of animal or food, and terms that incite undue fear, like “fatal” and “epidemic.”
“You can’t track something you can’t name,” said Oliver Pybus, an Oxford evolutionary biologist who helped design the Pango system.
Scientists name variants when changes in the genome coincide with new outbreaks, but they draw attention to them only if there is a change in their behavior — if they transmit more easily, for instance (B.1.1.7, the variant first seen in Britain), or if they at least partly sidestep the immune response (B.1.351, the variant detected in South Africa).
Encoded in the jumbled letters and digits are clues about the variant’s ancestry: The “B.1,” for instance, denotes that those variants are related to the outbreak in Italy last spring. (Once the hierarchy of variants becomes too deep to accommodate another number and dot, newer ones are given the next letter available alphabetically.)