Low transmission in household contacts of patients with MERS-CoV

1. Of the 280 household contacts linked with 26 index cases of Middle East respiratory syndrome coronavirus (MERS-CoV) infection, 12 probable cases of secondary transmission were identified. 

2. The risk of secondary transmission likely differs in different situations; for example, transmission may be higher in nosocomial outbreaks.

Evidence Rating Level: 4 (Poor) 

Study Rundown: MERS-CoV was first identified in Saudi Arabia in 2012. There are over 800 laboratory-confirmed cases, with 288 fatalities as of July 2014. While much effort has been devoted to better characterizing MERS-CoV, there is still a limited understanding of its epidemiologic features. The purpose of this study was to assess the rate of silent or subclinical infection after exposure to cases of MERS-CoV infection. This cross-sectional study tested 280 household contacts of 26 index patients. Using reverse-transcriptase-polymerase-chain-reaction (RT-PCR) and serologic analysis, 12 probable cases of secondary transmission were identified. Notably, the rates of secondary transmission may be much different in other circumstances such as nosocomial outbreaks.

Click to read the study, published today in NEJM

Relevant Reading: Hospital outbreak of Middle East Respiratory Syndrome coronavirus

In-Depth [cross-sectional study]: This cross-sectional study examined household contacts of 26 index patients with clinically-apparent MERS-CoV infections. Index patients were identified as patients who were hospitalized with bilateral pneumonia and had MERS-CoV detected in respiratory samples through RT-PCR. All individuals living with these index patients participated in this investigation by providing pharyngeal swab specimens and primary serum samples. A small subset of the population also provided follow-up serum samples for further analysis. A total of 12 probable cases of secondary transmission were identified (4%; 95% confidence interval, 2 to 7). Of these, 7 were found to be positive through RT-PCR on pharyngeal swabs while 5 cases were identified through serologic analysis (i.e., recombinant ELISA and immunofluorescence assays).

Image: PD

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