Via NEJM, an editorial: Person-to-Person Spread of the MERS Coronavirus — An Evolving Picture. Excerpt:
Approximately 1 year ago, a novel coronavirus, the Middle East respiratory syndrome coronavirus (MERS-CoV), was first identified in the Journal as the causative agent of a lethal pneumonia in several patients in the Middle East.1 As of July 10, 2013, a total of 80 cases have been identified in the Middle East (Saudi Arabia, Jordan, Qatar, and the United Arab Emirates), Europe (United Kingdom, France, Italy, and Germany), and North Africa (Tunisia), with a case fatality rate of 56%.
Since this coronavirus is a close relative of the virus that caused the severe acute respiratory syndrome (SARS), a short-lived but alarming epidemic in 2002–2003 that resulted in approximately 8000 cases and 800 deaths, governmental, public health, clinical, and laboratory authorities all mobilized rapidly to respond to the new virus outbreak.
Soon after the identification of MERS-CoV, information about its genomic sequence and organization, species tropism, and host-cell receptor (dipeptidyl peptidase 4) was published.2,3 These initial studies did not identify the source of this newly identified virus, nor did they reveal whether MERS-CoV could be transmitted from human to human, a requirement for designation as an epidemic disease.
In this issue of the Journal, Assiri et al.4 describe the largest outbreak of MERS-CoV infection thus far, showing that the virus is transmitted from human to human. This outbreak occurred in several hospitals in the governorate of Al-Hasa in eastern Saudi Arabia, with transmission probably occurring in dialysis units, intensive care units, and wards. Most patients had underlying diseases, with a remarkable number (17 of 23) having diabetes.
In addition to showing that human-to-human transmission occurred frequently, the relatively large number of patients infected in this outbreak made it possible to define characteristics of the infection, such as the incubation time (5.2 days) and the serial interval (7.6 days). As seen in the SARS epidemic, there was variability in the numbers of patients infected by each index patient, with 1 patient transmitting virus to 7 contacts; superspreading events, in which a few patients infected large numbers of contacts, were critical factors in SARS reaching epidemic proportions.
The study by Assiri et al. shows that MERS-CoV has the potential to spread widely within health care settings, infecting primarily other patients but also health care workers and family contacts, although to a lesser extent. Patients with diabetes or chronic renal failure appear to be at especially high risk for severe MERS-CoV infection, but whether these coexisting conditions represent true risk factors or whether these patients happened to be preferentially exposed to index cases is not known, given the relatively small number of infected patients.
Also unclear from this study is the extent to which MERS-CoV infection is a systemic disease. Acute renal failure developed in several patients with the infection,1,5-7 possibly reflecting a high level of dipeptidyl peptidase 4–receptor expression in the kidney. However, in the absence of tissue samples obtained at surgery or autopsy, it has been difficult to determine the extent to which kidneys or other organs are infected.
Although the report by Assiri et al., as well as others in the Journal and elsewhere,6,7 indicates that human-to-human transmission occurs, at least in the context of close contact, many additional questions related to the transmission of MERS-CoV and its ability to reach epidemic proportions are unanswered.The article discussed in this editorial is Hospital Outbreak of Middle East Respiratory Syndrome Coronavirus. Meanwhile, the KSA Ministry of Health hasn't posted any updates since July 18.
