The world would get massively overpopulated very quickly.
Diseases maintain the balance of us with nature, if we eliminate them we are going to run out of food fast.
The limit is ultimately set by thermodynamics and the need to dissipate waste heat to space. This limit is around 1 trillion people, but this likely requires food be artificially synthesized. Using conventional agriculture, a global limit of 150 billion was set (in a 1979 study referenced in the 1985 book "The Global Possible", page 217), or 47 billion with a US-like diet. Nitrous oxide emission from agriculture is likely to be a long term concern, as this powerful greenhouse gas accumulates.
As always, please do not interpret these statements as advocacy of these outcomes.
This is where ai currently falls down. It can’t do new analysis.