In every epidemic, some die, others become ill and recover, and the luckiest live through infection without symptoms. In today’s pandemic, we are seeing this play out. Although the initial epidemiological data show that COVID-19 is more severe in older people, men and those with pre-existing conditions such as heart and lung disease, not everyone with severe disease has these risk factors. And not everyone at risk has the same symptoms, prognosis or outcome.
Why do people manifest such differences? And why is it not possible to predict an individual’s experience?
In past epidemics, death and survival were attributed to providence or fortune. Modern medicine and science provide a better understanding of why infection can lead to such different outcomes. Among individuals in the same risk group — the same age, say — differences in infection outcome can result from five different variables outside their control.