Middle East Respiratory Syndrome (MERS) is an illness caused by a virus (more specifically, a coronavirus) called Middle East Respiratory Syndrome Coronavirus (MERS-CoV). Most MERS patients developed severe acute respiratory illness with symptoms of fever, cough and shortness of breath. About 3 to 4 out of every 10 patients reported with MERS have died.
Health officials first reported the disease in Saudi Arabia in September 2012. Through retrospective (backward-looking) investigations, health officials later identified that the first known cases of MERS occurred in Jordan in April 2012. So far, all cases of MERS have been linked through travel to, or residence in, countries in and near the Arabian Peninsula. The largest known outbreak of MERS outside the Arabian Peninsula occurred in the Republic of Korea in 2015. The outbreak was associated with a traveler returning from the Arabian Peninsula.
MERS-CoV has spread from ill people to others through close contact, such as caring for or living with an infected person.
MERS can affect anyone. MERS patients have ranged in age from younger than 1 to 99 years old.
CDC continues to closely monitor the MERS situation globally and work with partners to better understand the risks of this virus, including the source, how it spreads, and how infections might be prevented. CDC recognizes the potential for MERS-CoV to spread further and cause more cases globally and in the U.S. We have provided information for travelers and are working with health departments, hospitals, and other partners to prepare for this.
Symptoms & Complications
Most people confirmed to have MERS-CoV infection have had severe acute respiratory illness with symptoms of:
- shortness of breath
Some people also had gastrointestinal symptoms including diarrhea and nausea/vomiting. For many people with MERS, more severe complications followed, such as pneumonia and kidney failure. About 3 to 4 out of every 10 people reported with MERS have died. Most of the people who died had an underlying medical condition. Some infected people had mild symptoms (such as cold-like symptoms) or no symptoms at all; they recovered.
Based on what researchers know so far, people with pre-existing medical conditions (also called comorbidities) may be more likely to become infected with MERS-CoV, or have a severe case. Pre-existing conditions from reported cases for which we have information have included diabetes; cancer; and chronic lung, heart, and kidney disease. Individuals with weakened immune systems are also at higher risk for getting MERS or having a severe case.
Based on information we have to date, the incubation period for MERS (time between when a person is exposed to MERS-CoV and when they start to have symptoms) is usually about 5 or 6 days, but can range from 2 to 14 days.
MERS-CoV, like other coronaviruses, is thought to spread from an infected person’s respiratory secretions, such as through coughing. However, the precise ways the virus spreads are not currently well understood.
MERS-CoV has spread from ill people to others through close contact, such as caring for or living with an infected person. Infected people have spread MERS-CoV to others in healthcare settings, such as hospitals. Researchers studying MERS have not seen any ongoing spreading of MERS-CoV in the community.
All reported cases have been linked to countries in and near the Arabian Peninsula. Most infected people either lived in the Arabian Peninsula or recently traveled from the Arabian Peninsula before they became ill. A few people became infected with MERS-CoV after having close contact with an infected person who had recently traveled from the Arabian Peninsula. The largest known outbreak of MERS outside the Arabian Peninsula occurred in the Republic of Korea in 2015 and was associated with a traveler returning from the Arabian Peninsula.
Public health agencies continue to investigate clusters of cases in several countries to better understand how MERS-CoV spreads from person to person.
Currently, there is no vaccine to prevent MERS-CoV infection. The U.S. National Institutes of Health is exploring the possibility of developing one.
CDC routinely advises that people help protect themselves from respiratory illnesses by taking everyday preventive actions:
- Wash your hands often with soap and water for 20 seconds, and 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 personal contact, such as kissing, or sharing cups or eating utensils, with sick people.
- Clean and disinfect frequently touched surfaces and objects, such as doorknobs.
There is no specific antiviral treatment recommended for MERS-CoV infection. Individuals with MERS often receive medical care to help relieve symptoms. For severe cases, current treatment includes care to support vital organ functions.
People Who May Be at Increased Risk for MERS
Recent Travelers from the Arabian Peninsula
If you develop a fever and symptoms of respiratory illness, such as cough or shortness of breath, within 14 days after traveling from countries in or near the Arabian Peninsula you should call ahead to a healthcare provider and mention your recent travel. Until your healthcare provider says it’s okay, stay home from work or school and delay future travel to reduce the possibility of spreading illness to others.
Close Contacts of an Ill Traveler from the Arabian Peninsula
If you have had close contact with someone within 14 days after they traveled from a country in or near the Arabian Peninsula and the traveler has/had fever and symptoms of respiratory illness, such as cough or shortness of breath, you should monitor your health for 14 days, starting from the day you were last exposed to the ill person.
If you develop fever* and symptoms of respiratory illness, such as cough or shortness of breath, you should call ahead to a healthcare provider and mention your recent contact with the traveler. Until your healthcare provider says it’s okay, stay home from work or school and delay future travel to reduce the possibility of spreading illness to others.
Close Contacts of a Confirmed Case of MERS
If you have had close contact with someone who has a confirmed MERS-CoV infection, you should contact a healthcare provider for an evaluation. Your healthcare provider may request laboratory testing and outline additional recommendations, depending on the findings of your evaluation and whether you have symptoms. You most likely will be asked to monitor your health for 14 days, starting from the day you were last exposed to the ill person. Watch for these symptoms:
- Fever. Take your temperature twice a day.
- Shortness of breath
- Other early symptoms to watch for are chills, body aches, sore throat, headache, diarrhea, nausea/vomiting, and runny nose.
If you develop symptoms, call ahead to your healthcare provider as soon as possible and tell him or her about your possible exposure to MERS-CoV so the office can take steps to keep other people from getting infected. Ask your healthcare provider to call the local or state health department.
Healthcare Personnel Not Using Recommended Infection-Control Precautions
Healthcare personnel should adhere to recommended infection control measures, including standard, contact, and airborne precautions, while managing symptomatic close contacts, patients under investigation, and patients who have probable or confirmed MERS-CoV infections. Recommended infection control precautions should also be utilized when collecting specimens.
Healthcare personnel who had close contact with a confirmed case of MERS while the case was ill, if not using recommended infection control precautions (e.g. appropriate use of personal protective equipment), are at increased risk of developing MERS-CoV infection and should be evaluated and monitored by a healthcare professional with a higher index of suspicion.
People with Exposure to Camels
MERS-CoV has been found in some camels, and some MERS patients have reported contact with camels. However, we do not know exactly how people become infected with MERS-CoV—many people with MERS have had close contact with a person sick with MERS.
The World Health Organization has posted a general precaution for anyone visiting farms, markets, barns, or other places where animals are present. Travelers should practice general hygiene measures, including regular handwashing before and after touching animals, and avoid contact with sick animals. Travelers should also avoid consumption of raw or undercooked animal products.
The World Health Organization considers certain groups to be at high risk for severe MERS; these groups include people with diabetes, kidney failure, or chronic lung disease and people who have weakened immune systems. The World Health Organization recommends that these groups take additional precautions:
- Avoid contact with camels
- Do not drink raw camel milk or raw camel urine
- Do not eat undercooked meat, particularly camel meat