More than a decade after Middle East respiratory syndrome coronavirus (MERS-CoV) was first identified, the world still has a limited view of where it is circulating. Two studies published this month in the CDC’s Emerging Infectious Diseases look at why. One audits the public genomic record. The other tests whether COVID-19 exposure can make antibody tests give misleading results.
MERS-CoV is carried by dromedary camels and spills over into people intermittently. As of September 29, 2026, health authorities worldwide had reported 2,649 cases, including 960 deaths, according to the European Centre for Disease Prevention and Control’s running tally of WHO and national data, a fatality rate of about 36%. Saudi Arabia accounts for about 84% of cases. Reports have declined sharply in recent years, and ECDC noted earlier this year that newly reported cases are at their lowest level since 2014. No licensed vaccine or therapeutic exists.
A Genomic Record With Large Blind Spots
A WHO-led team, working with collaborators in Saudi Arabia, the United Arab Emirates (UAE) and elsewhere, analyzed 807 MERS-CoV genomes from people and camels, collected between 2012 and 2025 and shared in public databases. The record is lopsided. Saudi Arabia supplied 52.5% of the genomes, and Saudi Arabia and the UAE together supplied 75%. The WHO African Region supplied just 8.3%, despite large camel populations and active camel trade.
That imbalance extends to camel sampling. Of 27 countries with more than 100,000 camels, only 10 had any camel-derived genomes. Saudi Arabia had a median of 353 genomes per million camels, compared with 7 in Kenya.
Timing is another problem. The gap between collecting a sample and publicly sharing its sequence has grown over time and sometimes exceeds five years, which limits how useful the data are for real-time awareness.
The dataset reflects what has been shared, not the full diversity of the virus. Camel counts do not separate dromedaries from Bactrian camels, and trade data show animal movement, not infection. Still, the authors point to camel markets and trade routes linking Africa and the Arabian Peninsula as places where coverage is thin. They also note recent detections of clade B, a lineage usually found on the Arabian Peninsula, in camels in Egypt and Kazakhstan. Clade C, found in East African camels, makes up about 10% of the dataset and has no officially reported local human cases, which may be a case of underreporting.
When COVID-19 Immunity Complicates MERS Testing
The second study, from Erasmus Medical Center in the Netherlands, addresses a different problem. Where molecular testing is unavailable or incomplete, antibody tests are used to find past MERS-CoV infections. But COVID-19 infection or vaccination can produce antibodies that react with MERS-CoV, which could cause false positives.
The team tested blood serum from people in the Netherlands, who were assumed never to have been exposed to MERS-CoV. Participants had recovered from mild COVID-19, recovered from severe COVID-19, or received multiple COVID-19 vaccine doses. Every group showed some antibody binding to the MERS-CoV spike protein, mostly to a region called S2 that the two viruses share. The strongest cross-reactivity followed severe COVID-19. Eleven samples from that group neutralized MERS-CoV, meaning the antibodies could block the virus in the lab, and one sample from the mild group did so partially. Serum from vaccinated participants did not neutralize it.
The practical finding is that cross-reactivity can largely be screened out. Pairing a binding test aimed at a different region, called S1, with a neutralization assay left only one sample from the COVID-19-exposed groups testing positive on both. A commercial S1 test flagged none of the samples it was run on, though the authors note that a higher cutoff costs sensitivity and could miss real, low-level responses. They advise against using the nucleocapsid protein as the test target, because SARS-CoV-2 infection can induce antibodies that bind it. WHO’s 2018 guidance recommends confirming screening results with a neutralization test but does not say which antigen to use.
What the Two Studies Mean Together
Together, the papers suggest that MERS-CoV surveillance is limited by the quality of the data as well as the amount of testing. Genomes come mostly from places where sampling is already strong and arrive late. Antibody tests, meanwhile, can pick up immune responses left by COVID-19 and mistake them for past MERS-CoV infection, a risk that grows as more people have had COVID-19 or been vaccinated. Because antibody testing is often used where molecular testing is unavailable or incomplete, the finding that S1 binding paired with neutralization is more specific has practical weight.
The authors of both studies point to more representative sampling and more careful test design as the way to make surveillance data usable for early warning and risk assessment.
Sources and further reading:
Otieno JR, Albarraq AM, Selvaraj FA, et al. Global Genomic Surveillance of Middle East Respiratory Syndrome Coronavirus. Emerging Infectious Diseases. October 13, 2026.
te Marvelde MR, Mykytyn AZ, Raadsen MP, et al. Serologic Testing for Middle East Respiratory Syndrome Coronavirus and SARS-CoV-2 Cross-Reactive Immune Responses, the Netherlands. Emerging Infectious Diseases. October 13, 2026.
MERS-CoV worldwide overview — European Centre for Disease Prevention and Control
This article was researched and sourced by Global Biodefense editors and reported with Claude AI assistance for drafting and editing.