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Middle East Respiratory Syndrome (MERS)

Middle East Respiratory Syndrome (MERS) is a severe respiratory illness that mainly involves the upper respiratory tract. It causes fever, coughing, and shortness of breath. About 35% of people who have gotten this illness have died. Some people only have mild symptoms.

MERS is caused by the Middle East Respiratory Syndrome Coronavirus (MERS-CoV). Coronaviruses are a family of viruses that can cause mild to severe respiratory infections. MERS was first reported in Saudi Arabia in 2012 and then spread to many countries. Most cases were spread from people who traveled to the Middle Eastern countries.

To date, there have only been 2 cases of MERS in the United States. They were in people traveling to the United States from Saudi Arabia and diagnosed in 2014. The virus poses a very low risk to people in the United States.

How MERS Spreads

The MERS virus comes from MERS-CoV virus mainly spreads from animals to humans. The virus has been found in camels, and exposure to camels is a risk factor for MERS.

The virus can spread between people in close contact. This includes health care workers who care for people with MERS.

The incubation period of this virus is not precisely known. This is the amount of time between when a person is exposed to the virus and when symptoms occur. The average incubation period is about 5 days, but there are cases that occurred between 2 to 14 days after exposure.

MERS Symptoms

The main symptoms are:

Less common symptoms include coughing up blood, diarrhea, and vomiting.

Some people infected with MERS-CoV had mild symptoms or no symptoms at all. Some people with MERS have developed pneumonia and kidney failure. About 3 to 4 out of every 10 people with MERS have died. Most of those who developed severe illness and died had other health problems that weakened their immune system.

Right now, there is no vaccine for MERS and no specific treatment. Supportive care is given.

Steps to Help Prevent MERS

If you plan to travel to one of the countries where MERS is present, the Centers for Disease Control Prevention (CDC) advises taking the following steps to prevent illness.

  • Wash your hands often with soap and water for 20 seconds. Help young children do the same. If soap and water are not available, use an alcohol-based hand sanitizer.
  • Cover your nose and mouth with a tissue when you cough or sneeze then throw the tissue in the trash.
  • Avoid touching your eyes, nose, and mouth with unwashed hands.
  • Avoid close contact, such as kissing, sharing cups, or sharing eating utensils, with sick people.
  • Clean and disinfect frequently touched surfaces, such as toys and doorknobs.
  • If you come in contact with animals, such as camels, wash your hands thoroughly afterward. It has been reported that some camels carry the MERS virus.

For more information about MERS, you can visit the following websites.

Centers for Disease Control and Prevention website. Middle East Respiratory Syndrome (MERS) -

World Health Organization website. Middle East Respiratory Syndrome (MERS-CoV) -

Alternative Names

Middle East Respiratory Syndrome Coronavirus; MERS-CoV; Coronaviruses; CoV


Centers for Disease Control and Prevention website. Middle East Respiratory Syndrome (MERS): frequently asked questions and answers. Updated August 2, 2019. Accessed March 22, 2024.

Havers FP, Kirking H, Plumb ID. Pre-2019 coronaviruses. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 334.

Perlman S, McIntosh K. Coronaviruses, including severe acute respiratory syndrome (SARS) and Middle East Respiratory Syndrome (MERS). In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 155.

World Health Organization website. Middle East respiratory syndrome coronavirus (MERS-CoV). Accessed March 22, 2024.

Review Date 3/16/2024

Updated by: Jatin M. Vyas, MD, PhD, Associate Professor in Medicine, Harvard Medical School; Associate in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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