Chronic lung disease (OR = 0.78 with p < 0.001 for the HDL group, and OR = 0.76 with p = 0.011 for the apoA1 group), obesity (OR = 0.68 for the HDL group, and OR = 0.58 for the apoA1 group; both p < 0.001) and HIV (OR = 0.65 for the HDL group, and OR = 0.28 for the apoA1 group; both p < 0.001) significantly reduced the risk of infection, while uncomplicated diabetes was a risk factor for infection (OR = 1.24 with p < 0.001 for the HDL group, and OR = 1.57 with p = 0.001 for the apoA1 group) in both groups. The gene discussed is APOA1; the disease is obesity due to melanocortin 4 receptor deficiency.