For COVID-19, age and sex appear to be strong predictors of who lives and who dies. Jeremy Rossman writes in The Conversation that the fatality rate for the disease is estimated to be 0.66%, according to data from China. In other words, 0.66% of people who are formally diagnosed with COVID-19, die. But the rate varies dramatically for different age groups, ranging from 0.0016% for children under ten to 7.8% in people over 79. Similar rates are seen in New York city. One explanation is that the ability of the human immune system to fight off pathogens declines over time and is significantly reduced in those over 70. But it is also possible that the reason why more men and elderly people are dying from COVID-19 is more simple. We know that the risk of fatal COVID-19 disease is almost twice as great if the person has underlying health conditions. Most of these health conditions show increasing prevalence with age, such as hypertension, which increases in occurrence from 7.5% in those under 40 to over 63% in those over 60. This increasing rate of predisposing health conditions could directly increase the risk of severe COVID-19 disease.