It is believed that the earliest strains of HIV to infect humans were milder and sometimes stopped by the immune system. Over the years, the virus grew hardier, mutated, and recombined. By the early 80’s, when it was first identified, it had practically become a death sentence.
There is some evidence that AIDS made the rounds in Europe following World War II, predicated on a wave of children dying from PCP, a disease which only afflicts those with weakened immune systems. Its presence is almost a sure sign that the patient has AIDS. A Dutch researcher traced the epidemic to the Baltic port city of Danzig, then found it spread throughout the continent. It is believed that the disease spread by the then relatively common practice of reusing needles. Surprisingly, approximately only one-third of the children died, suggesting the virus they contracted had not yet changed into the fully lethal version we recognize today.