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MERS

MERS - Photo Credit: NIH-NAID
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Background

A veterinarian collects a blood sample from a camel during an investigation into the first reported MERS-CoV case in Haramout, Yemen. Scientists suspect that camels are infected with MERS-CoV by bats, and then pass the virus to humans.

A veterinarian collects a blood sample from a camel during an investigation into the first reported MERS-CoV case in Haramout, Yemen. Scientists suspect that camels are infected with MERS-CoV by bats, and then pass the virus to humans.

Photo Credit: CDC/Awadh Mohammed Ba Saleh

The current body of evidence suggests that MERS is a zoonotic disease (a disease that normally exists in animals but that can infect humans) resulting from infection with MERS-CoV. Recognition of the first human coronavirus occurred in the mid-1960s. Since that time, six human coronaviruses have been identified, including MERS-CoV.1

MERS is a seasonal disease; however, there are cases reported throughout the year.2 Initial cases of MERS occurred in April and June 2012. More cases followed in April 2013 and May 2014. The most recent outbreak began in South Korea in May 2015.

The confirmed source and manner of transmission of MERS-CoV to humans is unknown.3,4 Scientists suspect that bats are a reservoir for the virus with subsequent transmission to camels and then to humans.5 MERS-CoV has been isolated only in one bat and camels are the only animals infected with a strain of the virus similar to that found in humans.6,7 Tests in other animals (e.g., wild birds, sheep, cows, water buffalo, swine, and goats) for antibodies to MERS-CoV have all been negative as of the time this page was last updated.8

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.9 CDC recommends that standard, contact and airborne precautions be used in healthcare settings to prevent transmission of MERS-CoV. OSHA's guidance follows similar principles in recommending prevention and control methods for other workers who may have occupational exposure to MERS-CoV.

Contact transmission can be direct or indirect. With direct contact, viral transmission occurs person-to-person. With indirect contact, transmission occurs through the transfer of infectious material or virus particles to an object or surface that a susceptible individual then touches. A study conducted in 2013 on the stability of the MERS-CoV virus under different temperature and humidity conditions suggested possible MERS-CoV transmission through fomites (inanimate objects or substances that can transmit infection).10 To date, transmission through fomites has not been verified. Questions also remain about the possible infectiousness of other body fluids or clinical samples, including feces.11

Airborne transmission results from inhalation of particles. It is thought to occur through close contact between patients and healthcare workers, and within families.12,13,14 Certain medical procedures (i.e., aerosol-generating procedures) and biological processes may aerosolize infectious particles that can deposit along the respiratory tract when they are inhaled, contributing to viral transmission.

Currently, the droplet transmission of MERS-CoV has not been confirmed. Droplet transmission results from release of an infectious agent during coughing, sneezing or talking, and when the droplets come into direct contact with the eyes, nose or mouth of a susceptible individual.

Transmission of the virus is more likely when infection prevention and control practices are inadequate. In the South Korean outbreak, delayed and poor hospital infection control, along with other factors, likely facilitated the rapid increase in cases, including many infections among healthcare workers.

Mutation is a concern from a public health perspective, as MERS-CoV would likely become more adaptive to community-wide transmission. With the most recent outbreak, the virus does not appear to be mutating.15

Additional information on coronaviruses is available on the U.S. Department of Health and Human Services (HHS), Centers for Disease Control and Prevention (CDC) Coronavirus web site.


1 Centers for Disease Control and Prevention, U.S. Department of Health and Human Services, "About Coronavirus."

2 World Health Organization, WHO-convened Laboratory Experts for MERS-CoV, "Preliminary analysis of Middle East respiratory syndrome coronavirus (MERS-CoV) sequences from Korea and China".

3 A.N. Alagaili, T. Briese, N. Mishra, V. Kapoor, S. Sameroff, E. de Wit, et al., "Middle East respiratory syndrome coronavirus infection in dromedary camels in Saudi Arabia," mBio, 5, 2, e00884-14.

4 World Health Organization, WHO-convened Laboratory Experts for MERS-CoV, "Preliminary analysis of Middle East respiratory syndrome coronavirus (MERS-CoV) sequences from Korea and China".

5 California Department of Public Health, "Middle East Respiratory Syndrome Coronavirus (MERS-CoV) Quicksheet".

6 World Health Organization, WHO-convened Laboratory Experts for MERS-CoV, "Preliminary analysis of Middle East respiratory syndrome coronavirus (MERS-CoV) sequences from Korea and China".

7 Lin-fa Wang and Christopher Cowled, "Genomics," John Wiley and Sons, 2015, 140-147.

8 Centers for Disease Control and Prevention, U.S. Department of Health and Human Services, "Symptoms & Complications."

9 Centers for Disease Control and Prevention, U.S. Department of Health and Human Services, "Middle East Respiratory Syndrome (MERS) - About MERS - Transmission."

10 N. van Doremalen, T. Bushmaker, and V.J. Munster, "Stability of Middle East respiratory syndrome coronavirus (MERS-CoV) under different environmental conditions," Euro. Surveill., 18, 38 (2013).

11 A. Mailles, K. Blanckaert, P. Chaud, S. Van der Werk, B. Lina, V. Caro et al., " First cases of Middle East Respiratory Syndrome Coronavirus (MERS-CoV) infections in France: Investigations and Implications for the Prevention of Human-to-Human Transmission," Euro. Surveill., 18, 24 (2013).

12 Centers for Disease Control and Prevention, "Symptoms & Complications."

13 National Library of Medicine, "Middle East Respiratory Syndrome (MERS)."

15 Centers for Disease Control and Prevention, U.S. Department of Health and Human Services, "MERS Clinical Features."

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