Coronavirus – Credit CDC PHIL
We are just shy of three years since we first heard of a previously unidentified novel coronavirus discovered to be circulating in Saudi Arabia. News which came from a September 2012 letter posted in ProMed Mail (NOVEL CORONAVIRUS - SAUDI ARABIA: HUMAN ISOLATE) by Dr. Ali Mohamed Zaki - an Egyptian Virologist working In Saudi Arabia.
When it was first announced, MERS (then nCoV) seemed more a scientific curiosity than a public health threat.
Retrospective analysis showed the MERS coronavirus to have been involved in a pneumonia outbreak at a hospital in Jordan in April of that year (see Serological Testing Of 2012 Jordanian MERS Outbreak), and we saw a small handful of sporadic cases that fall.
Still, 2012 closed out with fewer than 10 confirmed cases (see WHO Coronavirus Update).
That number would increase 20-fold over the next twelve months – in part due to better surveillance and testing - with the global tally sitting at 187 cases by the end of 2013. The global tally would grow again to 960 by the end of 2014, and so far in 2015 we’ve added roughly 500 more cases.
Credit ECDC RRA July 31st, 2015
While 1400 cases and 500 deaths in three years pales in comparison to the Ebola crisis in West Africa, MERS-CoV – as a respiratory virus – has more built in `pandemic potential’ than do hemorrhagic fevers.
Also, MERS produces a wider spectrum of illness than Ebola, with both severe and mild (even asymptomatic) cases, which suggests documented cases may represent a fraction of the total burden of the disease. In November of 2013, we looked at a study that calculated that for every case identified, there were likely 5 to 10 that went undetected.
The origins of the virus are not fully understood, but serum analysis of dromedary blood samples going back 30 years shows the virus present in that species for decades (see EID Journal: Three Decades Of MERS-CoV Antibodies In Camels), while experiments by Colorado State University (see Back To The Camel `Shed’) show camels shed copious amounts of virus.
While likely only responsible for a small fraction of the total number of human cases, camel contact likely re-seeds the virus back into the community regularly. How often, and under what circumstances that happens, remains unknown.
And that’s the problem. After three years, we still know surprisingly little about the ecology and epidemiology of the MERS coronavirus. Deficits we’ve looked at often, including last May in WHO EMRO: Scientific Meeting Reviews MERS Progress & Knowledge Gaps.
While many cases have been linked to hospital spread, and camels are presumed to play some part in introduction of the virus to humans, for most community acquired cases the source of infection remains unknown.
Also unexplained are the lopsided demographics of infection (skewing predominately older, and male), with those under the age of 20 (40% of the Saudi Population) only representing about 2% of the cases.
Normally we’d get answers to these questions from a well mounted case-control study, where epidemiologists would compare laboratory-confirmed cases to a large number of controls, matched for age, sex, and by neighborhood. By examining their respective exposures against their outcomes, patterns of risk are often revealed.
But despite repeated promises (see KSA Announces Start To Long-Awaited MERS Case Control Study), for whatever reason, we’ve yet to see the results.
The recent exportation of a single MERS case to South Korea, where it precipitated 185 additional infections, along with the current outbreak in Riyadh just five weeks before the start of the Hajj, is a strong reminder that what we don’t know about MERS can hurt us.
The Koreans have promised a `white paper’ on their recent MERS outbreak, and I expect we’ll see a number of other papers published. After a shaky start, the Koreans showed commendable openness regarding their outbreak.
Sadly, the same cannot be said for the country at the epicenter of the MERS outbreak; Saudi Arabia.
Scientific papers have been slow to emerge, daily reporting on cases is both erratic and devoid of much needed detail, and without a proper case-control study, our understanding of the dynamics of MERS disease transmission remains murky at best.
While MERS doesn’t appear ready for pandemic prime time, it has also shown no signs of going away.
All of which leads up to an opinion piece, published online today in the Annals of Internal Medicine, arguing for better international scientific collaboration on MERS while its threat remains limited. I’ve only excepted the first paragraph, so follow the link to read it in its entirety.
Ideas and Opinions | 18 August 2015
Trish M. Perl, MD, MSc; and Connie Savor Price, MD
Ann Intern Med. 2015;163(4):313-314. doi:10.7326/M15-1395
This article was published online first at www.annals.org on 23 June 2015.
With the public riveted to the Ebola virus disease epidemic this past year, it is not surprising that the Middle East respiratory syndrome (MERS) has fallen off the radar. Time (1) identified the spread of the MERS virus as one of the top 10 underreported stories in 2013 and cited the low number of known reported cases as grossly understating the potential threat. Now, almost 3 years after the World Health Organization announced the first recognized human case of MERS, it has reemerged in the Middle East; however, it is overshadowed by Ebola and other new emerging infectious diseases. But with a rapidly evolving and new cluster of at least 172 cases in Korea—including 3 generations of transmission and 27 deaths as of 23 June 2015—it is imperative that we assess our progress to date in containing and understanding MERS (2).