FIGURE 2.

Alternate causal models are consistent with enrichment of bacterial secondary infections in fatal COVID-19 cases. We simulated cohorts of 1,000 hospitalized COVID-19-positive cases, constrained by the data of Zhou et al. (2020) ensure that 28% overall mortality and 15% of cases have culture-positive bacterial infection. The inset schematics summarize four distinct causal models for relationships between viral severity, V, bacterial severity, B, and patient death, D. In all scenarios, the mortality rate is greater when conditioned on bacterial infection, regardless of whether B is the sole direct cause of death (A), a partial cause of death (C,D), or not a direct cause of death (B).