Middle East respiratory syndrome (MERS)


MERS summary1-4

Pathogenic agent

Middle East respiratory syndrome coronavirus (MERS-CoV)


27 countries in the Middle East, Africa, and South Asia; 80% of cases reported in Saudi Arabia


Direct or indirect contact with infected dromedary camels; infrequent human-to-human contact within households and healthcare settings


  • Since outbreak first reported in 2012, 858 known deaths due to MERS-CoV and related complications
  • Case-fatality rate (CFR) up to 35%
  • MERS affects people of both sexes (65% of reported cases male) and all age groups, with more severe disease occurring in older people and those with weakened immune systems

The Middle East Respiratory Syndrome (MERS) is transmitted through contact with infected camels and people.1,2 The first case of MERS occurred in a man who was hospitalized with severe respiratory illness and later died of respiratory failure in Saudi Arabia in 2012.3 The cause of his illness was a novel coronavirus—the first highly pathogenic human coronavirus to emerge since the global scare caused by SARS-CoV in 2002—and was subsequently named MERS coronavirus (MERS-CoV).

Over 2,000 MERS-CoV infections have since been reported in many countries across the Middle East, Europe, North Africa, and Asia.3,4 Most cases are linked with travel to the Middle East region, and transmission within hospitals is common.1

Today, MERS-CoV persists in low numbers, is periodically introduced into human populations in sporadic outbreaks, and has the potential to reemerge in future pandemics.2,3

What characterizes MERS?

MERS affects people of all age groups, with more severe disease occurring in older people and those with weakened immune systems.3 Children may be less likely to develop severe MERS, but data on this are limited.

Although MERS-CoV infection does not always cause illness, about 33% of people with symptomatic disease experience severe pneumonia and acute respiratory distress syndrome (ARDS), and 35% die within days of developing symptoms (median, 11.5 days). Up to 50% of adult patients with symptomatic MERS are admitted to an intensive care unit (ICU), require mechanical ventilation, and do not show signs of improvement.3

Vaccines are currently under development

No specific, reliable antiviral drug or vaccine is approved for the treatment or prevention of MERS-CoV infections,3 so most patients are treated with supportive care (rest, fluids, and pain medications). Measures to prevent and control infection are critical to halt the spread of MERS, particularly in hospitals.1 Vaccines are considered the most cost-effective preventative measure that could be produced at a large enough scale to help prevent a serious outbreak. Several MERS-CoV vaccines spanning multiple platforms have been designed and are currently under clinical investigation.4 Safe and effective vaccines are required to help protect against possible future outbreaks of MERS-CoV and prevent potentially high fatalities.2,5

  1. Azhar EI, et al. The Middle East respiratory syndrome. Infect Dis Clin North Am. 2019;33:891–905.
  2. Memish ZA, et al. Middle East respiratory syndrome. Lancet. 2020;395:1063–1077.
  3. Chafekar A, Fielding BC. MERS-CoV: Understanding the latest human coronavirus threat. Viruses. 2018;1093.
  4. Schindewolf C, Menachery VD. Middle East respiratory syndrome vaccine candidates: cautious optimism. Viruses. 2019;11:74.
  5. Mubarak A, et al. Middle East respiratory syndrome coronavirus (MERS-CoV): infection, immunological response, and vaccine development. J Immunol Res. 2019;2019:6491738.