Transmissibility of MERS-CoV Infection in Closed Setting, Riyadh, Saudi Arabia, 2015

Abstract

To investigate a cluster of Middle East respiratory syndrome (MERS) cases in a women-only dormitory in Riyadh, Saudi Arabia, in October 2015, we collected epidemiologic information, nasopharyngeal/oropharyngeal swab samples, and blood samples from 828 residents during November 2015 and December 2015-January 2016. We found confirmed infection for 19 (8 by reverse transcription PCR and 11 by serologic testing). Infection attack rates varied (2.7%-32.3%) by dormitory building. No deaths occurred. Independent risk factors for infection were direct contact with a confirmed case-patient and sharing a room with a confirmed case-patient; a protective factor was having an air conditioner in the bedroom. For 9 women from whom a second serum sample was collected, antibodies remained detectable at titers >1:20 by pseudoparticle neutralization tests (n = 8) and 90% plaque-reduction neutralization tests (n = 2). In closed high-contact settings, MERS coronavirus was highly infectious and pathogenicity was relatively low.

Keywords: MERS-CoV; Middle East respiratory syndrome coronavirus; Riyadh; Saudi Arabia; human-to-human transmission; outbreak investigation; seroepidemiology; viruses.

Figure 1

Schematic of expatriate dormitory (the residence, buildings 1–12) and MERS-CoV infection attack rates (IARs), Riyadh, Saudi Arabia, 2015. Each building contained 2 villas on 3 floors. The distance between buildings is ≈5 m. During the initial investigation (October 2015), 8 residents were positive for MERS-CoV by PCR (indicated by black boxes); they lived in buildings 1B, 2A, and 5B. A vegetable garden separated buildings 3 and 10, and a convenience store (shop) separated buildings 6 and 7. IARs are shown as percentages inside each villa. MERS-CoV, Middle East respiratory syndrome coronavirus; PRNT, plaque-reduction neutralization test.

Figure 2

Epidemiologic curve for symptomatic laboratory-confirmed case-patients with Middle East respiratory syndrome coronavirus infection, Riyadh, Saudi Arabia, 2015. The curve includes only the 12 case-patients for whom symptom onset was reported, not the 7 case-patients for whom infection was serologically confirmed but no symptoms were reported in the preceding 4 weeks.