Photo Credit NIAID
#18,834
Up until January of 2020 the coronavirus we were most worried about was MERS-CoV, which since 2012 had infected more than 2,500 people (mostly in the Middle East), and had killed roughly 35% of confirmed cases.
Reporting on MERS-CoV from Saudi Arabia (and neighboring countries) has plummeted over the past 6 years (see chart below), although the reasons why are a bit vague.As with H5N1's CFR, this Case Fatality Rate is likely overestimated, since mild (and even asymptomatic cases) have likely gone unreported. But at the same time, it appears to be more pathogenic than COVID.
The `fog' of the COVID pandemic, social distancing, and even some partial immunity from COVID vaccination have all been suggested. We've even seen reluctance to share information by some affected nations.
Admittedly, detecting MERS cases isn't always easy. Over the past decade we've looked at many of the challenges of MERS-CoV surveillance, including:
EID Journal: Sensitivity and Specificity Of MERS-CoV Antibody Testing
AJIC:Intermittent Positive Testing For MERS-CoV
JIDC: Atypical Presentation Of MERS-CoV In A Lebanese Patient
Evaluation of a Visual Triage for the Screening of MERS-CoV Patients
A a 2016 study (see EID Journal: Estimation of Severe MERS Cases in the Middle East, 2012–2016) suggested that as much as 60% of severe Saudi MERS cases go undiagnosed.
It seems likely the number of undetected mild or asymptomatic cases is even greater.
Over the past six months we've seen a small, but noticeable, uptick in cases reported by Saudi Arabia. In March KSA reported 4 cases (2 from late 2024), and in May a WHO DON report added 9 more. In the past few days there are (as yet unverified) reports of an 11th case in KSA.
All of which brings us to a new research article in the Journal of Epidemiology and Global Health - published last week - on the changing epidemiology of MERS-CoV cases since its emergence in 2012.
Due to its length I've only posted the abstract and some excerpt. Follow the link to read it in its entirety. I'll have a bit more when you return.
Epidemiological Characteristics of MERS-CoV Human Cases, 2012- 2025
Research
Open access
Published: 06 August 2025
Volume 15, article number 103, (2025)
Mazin Barry
Abstract
Aim
To describe the epidemiological characteristics of Middle East respiratory syndrome coronavirus (MERS-CoV) human cases since the first reported case in 2012.
Methods
This is a retrospective descriptive epidemiological analysis of all laboratory-confirmed MERS-CoV human cases reported to the World Health Organization (WHO) from 2012 to May 2025. Cumulative cases globally, along with their demographics, comorbidities, epidemiological exposure, symptoms, hospital admissions, and mortality, were included. Descriptive analysis was used for the data.
Results
Between March 2012 and May 2025, a total of 2,626 laboratory-confirmed MERS-CoV human cases were reported to the WHO, with 947 (36.1%) resulting in deaths. The majority of cases occurred in the Kingdom of Saudi Arabia (KSA), with 2,217 (84.4%) human cases and 866 (39.1%) deaths.
Twenty-six other countries reported human cases, with the highest number occurring in South Korea, which reported 186 cases (7.1%). The highest number of cases occurred in 2014, with 662 (29.9%) cases, followed by 2015, with 453 (20.4%) cases.
Almost half of the cases in KSA (44.7%) were secondary infections, and most (83%) required hospital admission, with 39.7% requiring admission to intensive care unit. The most common comorbidities were diabetes mellitus, chronic heart disease, and chronic renal failure.
Between 2020 and the end of May 2025, 113 new human cases of MERS-CoV infection (4.3%) were reported, with the majority occurring in KSA. In 2025 alone, 10 new cases were reported, with two deaths. Secondary transmission occurred in 60% of these cases. Seven of the 10 cases were reported in April 2025 alone.
Conclusion
Between 2012 and May 2025, the majority of MERS-CoV infections occurred in the Kingdom of Saudi Arabia and had a high mortality, reaching 40%. Although most cases were reported between 2014 and 2015, new human cases are still ongoing and are increasing in 2025. Continued epidemiological investigation and surveillance are needed.
(SNIP)
The current study provides a brief description of the epidemiological characteristics of MERS-CoV human cases from its initial emergence in 2012 to the end of May 2025, highlighting various aspects and features of the disease, as well as gaps in current knowledge due to the ongoing spread of MERS-CoV and its potential to cause further outbreaks.
Many questions regarding the epidemiology of MERS-CoV, particularly within KSA, remain unanswered. Including what are the possible modes of transmission for MERS-CoV and associated transmission-based precautions that have been previously recommended and successful, and what is the duration of the infectious period of MERS-CoV?
Such questions and their answers require continued active surveillance, comprehensive epidemiological investigations, and continued reporting. Further epidemiological studies are warranted to help answer these questions.
Although dromedary camels are the primary animal reservoir for MERS - and direct or indirect contact are viewed as a major risk factor for infection - sporadic cases continue to show up in the community without any known exposures (camels, camel products, or known MERS cases).
A 2020 Perspective published in the EID Journal (see Middle East Respiratory Syndrome Coronavirus Transmission) reported that `. . . among 1,125 laboratory-confirmed MERS-CoV cases reported to WHO during January 1, 2015–April 13, 2018, a total of 157 (14%) had unknown exposure.'
In addition to its own evolutionary journey, some researchers worry MERS-CoV could recombine with SARS-CoV-2 (see Nature: CoV Recombination Potential & The Need For the Development of Pan-CoV Vaccines) and produce a more easily transmissible hybrid.
A reminder that nature's laboratory is open 24/7, and it is continually tinkering with a seemingly ever-growing array of zoonotic threats.
How likely that is to happen is a subject of considerable debate, but it appears to be at least theoretically possible.
MERS-CoV isn't the only non-COVID coronavirus on our watch list. A few recent blogs include:
Preprint: Human Cell adaptation of the Swine Acute Diarrhea Syndrome Coronavirus Spike Protein
J. Med. Virology: Potential Cross-Species Transmission Risks of Emerging Swine Enteric Coronavirus to Human Beings
Nature: Comparative Susceptibility of SARS-CoV-2, SARS-CoV, and MERS-CoV Across Mammals
A reminder that nature's laboratory is open 24/7, and it is continually tinkering with a seemingly ever-growing array of zoonotic threats.
