Was patient zero a concept used in epidemiology before 1980s HIV investigation?

Answer 1

No.

The concept of 'patient 0' has come to mean the first patient to spread a disease to a population. Another term for this concept is the "index patient". The concept of an index patient was in use before the 1980s, but the term patient 0 is directly associated with the HIV/AIDS epidemic in the 1980s.

However, this was not the original meaning. When monitoring HIV/AIDS, researchers recorded data by pen and paper (not computer). The patient who came to be known as patient 0 ("zero") was actually patient O ("oh"). The researchers used an alphabetically (A-Z) system to record new patients, not a numerical (0-9) one. At the time, patient O was considered to be "responsible" for spreading HIV/AIDS, although later analysis would reveal that he was not the true index patient.

However, the mistake of referring to him as Patient 0 (zero) instead of Patient O (oh) entered popular consciousness and is now the most frequently used term to refer to an Index Patient, especially in media and pop culture.

Additional reading: https://www.nytimes.com/2016/10/27/health/hiv-patient-zero-genetic-analysis.html