Fig. 2.

(a) Skeletal causal diagram of key events in initial and subsequent methicillin-resistant Staphylococcus aureus (MRSA) infections, applicable to all populations. (b) Propensity for colonization and infection added to panel (a). (c) The key immunological and medical parameters specific to HIV populations have been added to the skeletal causal diagram in panel (b). (d) Key epidemiological links between HIV and MRSA. Some factors (e.g. sexual risk factors) are likely directly causal for both HIV and for MRSA exposure. Other epidemiological factors (e.g. crowded living) are likely to be associated with HIV due to an undetermined underlying cause.