Epidemiology of MERS-CoV in Saudi Arabia, 2012-2025: a nationwide surveillance analysis

Middle East respiratory syndrome (MERS), caused by MERS coronavirus (MERS-CoV), is a severe zoonotic respiratory illness first identified in Saudi Arabia in 2012. Dromedary camels are the recognised reservoir, with human transmission occurring through animal exposure and, less commonly, person-to-person spread, particularly in healthcare settings.

To characterise all laboratory-confirmed MERS-CoV cases reported in Saudi Arabia from September 2012 to August 2025, examine trends across four periods defined by suspected-case definitions, and identify factors independently associated with mortality.

We analysed laboratory-confirmed cases in the national surveillance database by period and probable infection source. Case-fatality ratios (CFRs), 95% confidence intervals (CIs), and unadjusted odds ratios were calculated. Multivariable logistic regression assessed independent mortality associations using a prespecified model including period, age, sex, and infection source, and a fuller model additionally considering nationality, comorbidities, and pregnancy. Seasonality of primary cases was assessed using an annual harmonic term.

Among 2,219 cases, 1,545 (70%) were male, 1,566 (71%) Saudi nationals, and 608 (27%) aged ≥65 years. Overall, 1,211 (55%) were primary cases, including 172 (14%) reporting camel contact; 737 (33%) were healthcare-associated and 271 (12%) household- or community-associated. There were 867 deaths (CFR, 39%; 95% CI, 37%-41%). CFR declined from 65% in the earliest period to 32% in the most recent, although changing testing eligibility and ascertainment limit temporal comparisons. Older adults had the highest crude CFR. In the prespecified model, healthcare-associated infection among patients was associated with higher odds of death (aOR, 1.74; 95% CI, 1.15-2.65), while odds were lower among healthcare workers (aOR, 0.09; 95% CI, 0.05-0.17) and household contacts (aOR, 0.29; 95% CI, 0.18-0.48). No consistent seasonality was observed.

MERS-CoV epidemiology in Saudi Arabia reflects persistent zoonotic spillover, episodic healthcare-associated transmission, and substantial mortality, particularly among older adults. Sustained One Health surveillance, rapid detection, and rigorous infection prevention and control remain essential.