Thursday 12 September 2013

Middle East respiratory syndrome coronavirus cases amongst healthcare workers [UPDATED]

Click on image to enlarge. (a) the proportion of
MERS-CoV positives HCWs who have died (red) vs.
survived (blue), (b) the proportion of fatal cases (PFC; red) 
of MERS-CoV worldwide vs. the proportion of 
surviving cases (PSC; blue) (c) breakdown HCWs
as a proportion of all MERS-CoV cases (blue), HCW deaths 
as a proportion of all MERS cases (green) and HCW deaths
as a proportion of all MERS-CoV deaths.
With a lot of help from FluTrackers, the 2 of us have synced our lists to account for all the healthcare workers (HCWs) for which public data are available, that have been confirmed as MERS-CoV positive.

Some charts then.

We can see that HCWs make up approximately a sixth (18.2%; n=24) of all MERS-CoV cases.

Fatal infections in HCWs account for 2.3% (3/132) of all MERS-CoV cases (including living and deceased cases) and 5.4% of all MERS-CoV deaths worldwide are among HCWs (3/56). This last figure indicates that HCWs are at a relatively reduced risk of death from MERS-CoV infection when compared to other groups that have been infected.

For example:
NB: I have death data for 56 cases; age data for 125/132 cases; sex data for 120/132 cases); 27 comorbidities listed [underestimate]

  • 63% of MERS-CoV deaths have occurred among those older than 55-years (50% of deaths among those >60-years; 38% among those >65-years; 59% among those <65-years)
  • 46% of MERS-CoV deaths have occurred among males older than 55-years (38% among those>69-years; 30% among those >65-years; 45% among those <65-years)
  • 82% of deaths )n=46) and 83% of cases have occurred in the Kingdom of Saudi Arabia
  • 48% of MERS-CoV deaths occurred among those with comorbidities [this is an underestimate]So in the lower proportion of deaths represented by HCWs, while horrible in any proportion, may provide evidence to support that MERS-CoV is still not transmitting well, even in close quarters.

It may also mean that attending HCWs are adhering to good infection control and prevention practices. But it coudl just mean that we do not have data on all HCW infections/death and there are greater numbers of cases.

Finally, and perhaps most importantly, we should remember that HCWs may have some degree of resistance to disease caused by some viruses because of their constant exposure to patients with all manner of airway infections.

If HCWs may not show the same proportion of illness, but still become infected, they can act to spread cases among their contacts - patients and visitors. This was evident in the severe acute respiratory syndrome (SARS) outbreak where HCWs accounted for a fifth of all confirmed cases.1

In other words, even a few cases in HCWs could have major implications for nosocomial outbreaks. If an emerging virus, such as the MERS-CoV, is being frequently detected in association with healthcare settings, that scenario may already be happening.

Some literature..

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