So, how do the presence of comorbidities among MERS cases impact mortality and disease severity?
I attempted to answer this question by creating two new charts. Each chart splits up the 408 cases reported thus far into four categories:
1. Cases with comorbidities, prior to the onset of the current outbreak we’re seeing in the Middle East (3/20/14)
2. Otherwise healthy cases, prior to 3/20/14
3. Cases with comorbidities, on and after 3/20/14
4. Otherwise healthy case, on and after 3/20/14
The first graph looks at comorbidity and mortality:
It’s immediately apparent that otherwise healthy individuals – both pre and post March 20th – experience far lower mortality rates than their comorbid counterparts. We see here again that fatality is much lower now than it was before the onset of the current outbreak – among healthy and comorbid cases alike. However, it also seems that comorbidity has been having LESS of an impact on mortality since March 20th than before; there’s less of a difference between fatality rates among comorbid cases (19%) and healthy ones (12%).
The second graph looks at comorbidity and disease severity:
Perhaps unsurprisingly, the vast majority of asymptomatic MERS cases have occurred in otherwise healthy individuals. In fact, only 2 of the 69 total asymptomatic cases identified thus far have been individuals with documented pre-existing conditions. Overall though, it doesn’t look like the impact of comorbidity on disease severity has changed much pre and post March 20th.
1. Comorbidities have historically resulted in greater fatality among MERS cases. (However, this appears to be less the case in the outbreak we’re witnessing right now. )
2. Asymptomatic MERS cases rarely ever occur in individuals with comorbidities; they are most often found in otherwise healthy individuals.
While data are incomplete and imperfect, it seems to me as though comorbidities have a significant impact on the severity of the disease, as well as likelihood of mortality. Why is this the case? Until we better understand how MERS-CoV is transmitted and how it operates within the human body, it’s hard to say. We’ll just have to wait and see what happens next!
Note: Temporal data indicates date of onset, hospitalization, diagnosis, or public reporting.
Data Sources: KSA MoH & WHO