Middle East Respiratory Syndrome (MERS)

Outbreaks

Updated 03/13/25

Note: MERS is found cyclically in endemic regions.

March 13, 2025: From September 6, 2024, to February 28, 2025, four laboratory-confirmed cases of MERS-CoV infection, including two deaths, were reported by the Ministry of Health of the Kingdom of Saudi Arabia (KSA). (WHO, accessed 3/15/25, https://www.who.int/emergencies/disease-outbreak-news/item/2025-DON560)

See the chronology of MERS cases.

About Middle East Respiratory Syndrome (MERS)

Middle East Respiratory Syndrome (MERS) was discovered in 2012 in an individual who had been working with camels in Jeddah, Saudi Arabia. The WHO reports a global total of 2,613 laboratory-confirmed cases from April 2012 - May 2024, with 943 associated deaths. The majority of cases have occurred in Saudi Arabia, though there have been significant traveler-associated cases in Africa, Europe, Asia, and the United States.

MERS is a potentially serious respiratory illness caused by the Middle East Respiratory Syndrome Coronavirus (MERS-CoV). Although the route of transmission is not clearly understood, it is thought to be spread by close contact with infected dromedary (single hump) camels or the respiratory secretions of an infected person. The incubation period from time of exposure to the onset of symptoms is between 2-14 days with an average of 5-6 days. Currently, MERS is not thought to be contagious until the onset of symptoms, but precautions should be taken around individuals with a known exposure risk.

The case fatality rate of MERS CoV infections is approximately 36%, but this may be inflated due to the true surveillance data being unknown, as patients can have a wide spectrum of clinical symptoms. Some experience asymptomatic illness, while others have severe respiratory illness that can progress rapidly to pneumonia, respiratory failure, septic shock, and multiorgan failure.

Human-to-human transmission is possible, though rare unless in close contact, such as when providing unprotected care for a patient (WHO, accessed 5/15/25 https://www.who.int/en/news-room/fact-sheets/detail/middle-east-respiratory-syndrome-coronavirus-(mers-cov)).

The largest known outbreak of MERS outside the Arabian Peninsula occurred in the Republic of Korea in 2015 (CDC, accessed 5/17/22, https://www.cdc.gov/mers/about/). This occurred in a hospital, reinforcing the need for the U.S. healthcare system to prepare for such an event, however unlikely.

"Figure 3. Epidemic curve of laboratory-confirmed MERS-CoV human infections reported to WHO *as of 30 June 2019". WHO MERS-CoV Global Summary and Assessment of Risk, July 2019 (WHO/MERS/RA/19.1). Geneva, Switzerland: World Health Organization; 2019. Licence: CC BY-NC-SA 3.0 IGO.

Where to Start

Consult the CDC guidance here: https://www.cdc.gov/mers/about/.
Review NETEC’s online module on MERS-CoV.
"Patients in the U.S. Who Should Be Evaluated for MERS-CoV Infection." CDC. https://www.cdc.gov/mers/hcp/diagnosis-testing/.
See the WHO’s Middle East respiratory syndrome coronavirus (MERS-CoV) Fact Sheet.
See the WHO's Disease Outbreak News (DONs) for the latest updates on recent outbreaks of MERS.

Selected Resources

NETEC has curated essential MERS resources. If you have questions or need support, you can submit a request via the website or by emailing info@netec.org, and one of NETEC’s experts in special pathogens will respond.