Coronavirus – Credit CDC PHIL
This time last year we were looking at what appeared to be a large nosocomial outbreak of MERS in the Taif region (see Saudi Arabia – A MERS Surge?, although local officials had been denying any serious outbreak for weeks (see FluTrackers thread Saudi Arabia - Taif government denies coronavirus MERS epidemic in hospitals).
Today we’ve an analysis of that outbreak published in the CDC’s EID Journal, where we learn there were actually four local hospitals involved, 38 people were identified as infected, and 21 of those died.
Where this gets really interesting is that while these four facilities were originally thought to be separate clusters - genetic sequencing indicates they were all linked - even though no epidemiological link was established between these facilities. The authors write:
Similar gene sequences among patients unlinked by time or location suggest unrecognized viral transmission.
Elucidating further in the discussion section, they write:
Despite an exhaustive review of medical charts and interviews with HCP, we could establish no clear epidemiologic links among these facilities, suggesting that unrecognized cases of MERS-CoV infection might not have been captured by the existing surveillance system.
The ability for cases to pass undetected through the Saudi surveillance system has been the topic of more than one conversation in the past, but its biggest limitation is summed up by the authors who write:
Currently, the surveillance case definition for MERS in Saudi Arabia requires the presence of symptoms (13), and testing is reserved primarily for symptomatic patients, often with severe illness.
`Unrecognized cases’ not `captured by surveillance’ could reasonably be interpreted as including mild or asymptomatic carriers of the virus – something we’ve often seen reported - but for which we have precious little proof that they can transmit the virus (see Study: Possible Transmission From Asymptomatic MERS-CoV Case).
We have seen a large number of `primary’ community acquired cases for which there is no known risk exposure, which opens the door to the possibility of some limited `stealth’ transmission of the virus in the community by unidentified carriers of the virus (see The Community Transmission Mystery).
While the evidence remains circumstantial, today’s study would seem to add a bit more weight to the idea.
Given the technical nature of this study and that it really falls in his virological wheelhouse, I’m going to leave some meat on the bone here in hopes Ian Mackay will find time to write about it. In the meantime, the full study may be read at:
Volume 22, Number 1—January 2016
Abdullah Assiri, Glen R. Abedi , Abdulaziz A. Bin Saeed, Mutwakil A. Abdalla, Malak al-Masry, Abdul Jamil Choudhry, Xiaoyan Lu, Dean D. Erdman, Kathleen Tatti, Alison M. Binder, Jessica Rudd, Jerome Tokars, Congrong Miao, Hussain Alarbash, Randa Nooh, Mark Pallansch, Susan I. Gerber, and John T. Watson
Middle East respiratory syndrome (MERS) coronavirus (MERS-CoV) is a novel respiratory pathogen first reported in 2012. During September 2014–January 2015, an outbreak of 38 cases of MERS was reported from 4 healthcare facilities in Taif, Saudi Arabia; 21 of the 38 case-patients died.
Clinical and public health records showed that 13 patients were healthcare personnel (HCP). Fifteen patients, including 4 HCP, were associated with 1 dialysis unit. Three additional HCP in this dialysis unit had serologic evidence of MERS-CoV infection.
Viral RNA was amplified from acute-phase serum specimens of 15 patients, and full spike gene-coding sequencing was obtained from 10 patients who formed a discrete cluster; sequences from specimens of 9 patients were closely related.
Similar gene sequences among patients unlinked by time or location suggest unrecognized viral transmission. Circulation persisted in multiple healthcare settings over an extended period, underscoring the importance of strengthening MERS-CoV surveillance and infection-control practices.
Repeated introduction of MERS-CoV into healthcare facilities, resulting in transmission among patients, visitors, and HCP, has been a defining feature of MERS-CoV epidemiology since its emergence in 2012. Our investigation shows the persistence of MERS-CoV circulation in multiple healthcare settings over an extended period, despite lack of clearly defined epidemiologic links, and underscores the importance of identifying and monitoring exposed HCP, patients, and visitors.
MERS-CoV transmission in any healthcare facility should trigger increased vigilance among all healthcare facilities that could potentially share patients and staff. Increased understanding of epidemiologic links among identified patients during transmission events is needed to inform surveillance strategies and infection prevention and control.