Cases of Middle East respiratory syndrome coronavirus (MERS-CoV) have fallen drastically since the COVID-19 pandemic and have not rebounded as travel has returned to prepandemic levels.
However, U.S. testing has also decreased, according to a new CDC report.
The Need for More Data
There are many questions that remain regarding incidence of MERS-CoV, the authors write, many of which could be answered by continued surveillance efforts to better understand the virus (MMWR Morb Mortal Wkly Rep 2025;74[19]:313-320).
“The findings in this report guide MERS preparedness priorities, activities and future research,” said senior author Hannah L. Kirking, MD, a medical epidemiologist in the Coronavirus and Other Respiratory Viruses Division at the CDC’s National Center for Immunization and Respiratory Diseases.
MERS-CoV, a zoonotic virus transmitted sporadically from camels with limited subsequent human-to-human transmission, is mostly found in the Arabian Peninsula. In the United States, the last identified and confirmed MERS cases occurred during 2014. However, the virus does have pandemic potential.
Since MERS case reporting began in 2012 through December 31, 2023, a total of 2,608 MERS cases have been reported to the WHO. Among these, 84% occurred in Saudi Arabia.
While cases of MERS remained relatively stable from 2017 to 2019, with a median of 224 cases per year, reported MERS cases have declined substantially since the COVID-19 pandemic. A median of 17 cases per year have been reported between 2020 and 2023, and six cases were reported during 2023.
However, the cause of this drop in cases is unknown. Dr. Kirking said it requires further investigation.
U.S. Testing Declines
And while the number of travelers entering the United States from the Arabian Peninsula has returned to prepandemic levels, U.S. MERS-CoV testing declined during 2017 to 2023 and remains low relative to prepandemic years.
“The risk of MERS importation has returned to prepandemic levels, but U.S. testing levels have not,” Dr. Kirking said. “If the proportion of persons who meet persons under investigation (PUI) clinical criteria were to remain constant, U.S. MERS-CoV testing would be expected to be higher to mirror the increases in travelers. Epidemiologic testing and traveler data are indicators that are essential to guiding public health investigations and targeted readiness activities. Strengthening MERS-CoV surveillance and ongoing risk assessments are critical to support pandemic preparedness.”
Traveler and Virus Surveillance
In the United States, clinical and epidemiologic criteria to guide MERS-CoV testing were updated in 2024. “MERS continues to be a public health risk and targeted MERS surveillance is important to maintaining preparedness and promptly responding to potential cases,” Dr. Kirking said.
One strategy to be attuned to virus activity is to test travelers. “Traveler and testing data can inform the strategic allocation of testing capacity, and appropriate surveillance strategies,” Dr. Kirking said. “More specifically, jurisdictions with airports receiving high volumes of travelers from in or near the Arabian Peninsula are strategic locations for strengthening MERS testing and surveillance approaches.”
Other methods include surveillance evaluations, immunologic studies and genomic sequencing, Dr. Kirking said. “These types of studies can help elucidate if reported case declines are related to external factors, potential virologic changes or both.”
Dr. Kirking reported no relevant financial disclosures.
