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Critical care

Are hospital MERS outbreaks just like SARS?

Chowell G, Abdirizak F, Lee S, et al. · BMC medicine · 2015

Open access · cc by · source: Europe PMC

Comparing hospital clusters, MERS and SARS both ignite via early super-spreaders then drop below R=1 within 3–5 generations; a >100-case outbreak is about twice as likely for SARS (2% vs 1%), while MERS transmission is more heterogeneous.

How this study connects

Role on claims

Each row is a claim on a concept or method page where this paper supports, challenges, or qualifies the statement. Roles are hand-checked — not a model guess.

  • SupportsCritical Illnessconcept

    A mean reproduction number would describe none of these events.

    Transmission in healthcare settings is driven by rare individuals rather than by an average rate. Healthcare-linked MERS ranged from 43.5% to 100% of cases by outbreak, with Korea's index patient infecting 30 others and two second-generation patients infecting 80 and 23.

    Evidence for the claim as stated.

Study at a glance

Design
Computational / modelling — Comparative analysis of MERS vs SARS hospital outbreak trees plus 5,000 branching-process simulations per virus
N
N=8607 · 973 MERS and 7,634 SARS cases for HCW fractions; trees for Korea MERS n=186, Al-Hasa n=25, Singapore SARS n=188, Toronto n=90
Population
Laboratory-confirmed MERS and SARS cases in published hospital clusters (Saudi Arabia, South Korea, Singapore, Toronto, and other SARS sites)
Outcome
Exposure mix, reproduction number by generation, transmission heterogeneity, and probability of large nosocomial outbreaks

Structured fields used in claim comparison tables when every cited study has a complete layer.

Inspect source passages

Are hospital MERS outbreaks just like SARS?

These passages occur verbatim in the stored paper text. They support the points listed below; they do not verify every statement in the explanation.

Healthcare-linked MERS 43.5% to 100%.

ranging from 43.5 % for the nosocomial outbreak in Jeddah, Saudi Arabia, in 2014 to 100 %

>100-case probability 2% SARS vs 1% MERS.

Simulations indicate a 2-fold higher probability of occurrence of large outbreaks (>100 cases) for SARS than MERS (2 % versus 1 %)
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Key findings

Healthcare-linked MERS ranged from 43.5% (Jeddah 2014) to 100% (Al-Hasa and Korea). Korea’s index patient infected 30 others; two second-generation patients infected 80 and 23. HCWs were 13.4–13.5% of MERS vs 19–57% of SARS. Probability of >100 cases: ~2% SARS vs ~1% MERS; >186 MERS cases ~1%.

Methodology

Compiled exposure data and transmission trees for large MERS (South Korea 186; Al-Hasa 25; Jeddah) and SARS (Singapore 188; Toronto 90) hospital clusters, compared secondary-case distributions (negative binomial R and k), and simulated 5,000 outbreaks of each virus.

Limitations

Few fully resolved trees and reporting bias toward large clusters mean R and k are imprecise; simulations do not prove which infection-control rule would have stopped Korea 2015.

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