Credit CDC MERS Webpage
# 8733
To paraphrase Harry Truman (who was talking about economists), when it comes to figuring out the MERS virus, what we really need is a one-armed epidemiologist . . . someone who can’t say, `But, on the other hand . . .’
Practically at every turn, we are faced with some kind of inconsistency with this emerging disease, making it almost impossible to quantify its current, and future, public health risk.
While the vast majority of close contacts of known cases have tested negative, inexplicably the virus seems to thrive in a healthcare environment. We’ve seen numerous nosocomial clusters - and more than 100 healthcare workers infected – yet similar outbreaks in other community venues are rare.
Some family clusters have been reported, but they pale in comparison to hospital clusters, where strict infection control practices are supposedly in place.
Males outnumber females (particularly as index cases), and children and adolescents are only very rarely reported infected, despite being a large demographic in Middle East
And we haven’t a clue why either should be true.
Community-acquired cases continue to pop up, but their source remains largely unknown. Contact with camels, or camel products is suspected, but unproven. But in truth, there are likely several routes of infection in the community – including contact with mildly symptomatic or asymptomatic cases – making it difficult to pin down any one specific cause.
Two years into this slow-rolling epidemic, and we still know frustratingly little about its source, how the virus is transmitted, and where this epidemiological enigma will go from here.
By comparison, the SARS epidemic was over – and its source identified and quashed – eight months after it first emerged in China.
This high degree of uncertainty explains the wariness demonstrated by public health agencies around the world (see Hong Kong Unveils Their MERS-CoV Preparedness Plan) regarding this virus, even though the actual case count and death toll remains pretty low.
Today Lauren M Gardner and C Raina MacIntyre - both from The University of New South Wales ( Sydney, Australia) -take a closer look at this coronavirus conundrum in an open-access research note called:
Unanswered questions about the Middle East respiratory syndrome coronavirus (MERS-CoV)
Lauren M Gardner and C Raina MacIntyre
BMC Research Notes 2014, 7:358 doi:10.1186/1756-0500-7-358
Published: 11 June 2014
Abstract (provisional)
Background
The Middle East respiratory syndrome coronavirus (MERS-CoV) represents a current threat to the Arabian Peninsula, and potential pandemic disease. As of June 3, 2014, MERS CoV has reportedly infected 688 people and killed 282. We briefly summarize the state of the outbreak, and highlight unanswered questions and various explanations for the observed epidemiology.
Findings: The continuing but infrequent cases of MERS-CoV reported over the past two years have been puzzling and difficult to explain. The epidemiology of MERS-CoV, with many sporadic cases and a few hospital outbreaks, yet no sustained epidemic, suggests a low reproductive number. Furthermore, a clear source of infection to humans remains unknown. Also puzzling is the fact that MERS-CoV has been present in Saudi Arabia over several mass gatherings, including the 2012 and 2013 Hajj and Umrah pilgrimages, which predispose to epidemics, without an epidemic arising.
Conclusions
The observed epidemiology of MERS-CoV is quite distinct and does not clearly fit either a sporadic or epidemic pattern. Possible explanations of the unusual features of the epidemiology of MERS-CoV include sporadic ongoing infections from a non-human source; human to human transmission with a large proportion of undetected cases; or a combination of both. The virus has been identified in camels; however the mode of transmission of the virus to humans remains unknown, and many cases have no history of animal contact. A better understanding of the epidemiology of MERS CoV warrants further investigation.
The complete article is available as a provisional PDF. The fully formatted PDF and HTML versions are in production.
