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Summary of Assessment of Public Health Risk to Canada Associated with Middle East Respiratory Syndrome Coronavirus (MERS-CoV)

The risk assessment is reviewed on a regular basis and updated as required.

Updated: July 6, 2015

Risk Assessment

  • The public health risk posed by MERS-CoV to Canada is considered low based on available information at this time. The risk may change as new information arises.
  • MERS-CoV is considered a zoonotic virus that can lead to secondary infections among people. Many community-acquired infections are thought to be associated with direct or indirect contact with infected dromedary camels or camel-related products.
  • Some of the infections have occurred in clusters of close contacts or in health care settings. This provides good evidence of human-to-human transmission. However, no community wide transmission has been observed. While human-to-human transmission has been observed in households in affected countries, most human cases reported to date have resulted from human-to-human transmission in health care settings.
  • Additional cases of MERS-CoV infection are expected to be reported from the Middle East and Korea. Additionally, it is likely that cases will continue to be exported to other countries by tourists, travellers, guest, workers or pilgrims who might acquire infection following exposure to an animal or human source.

Event Summary

Since April 2012, 26 countries have reported cases of Middle East Respiratory Syndrome (MERS-CoV), including countries in the Middle East (Egypt, Iran, Jordan, Kuwait, Lebanon, Oman, Qatar, Saudi Arabia (KSA), United Arab Emirates (UAE) and Yemen; in Africa: Algeria, and Tunisia; in Europe: Austria, France, Germany, Greece, Italy, the Netherlands, Turkey and the United Kingdom; in Asia: China, the Republic of Korea, Malaysia, Philippines and Thailand; and in North America: the United States of America (USA). The majority of cases have been reported from KSA. There have been no cases identified in Canada.

Since 2012, the World Health Organization (WHO) has reported over 1,300 confirmed human cases, including over 400 deaths. For the latest updates on cases and deaths please visit the Global Alert and Response websiteExternal Link.

Since early 2014 three large outbreaks have been reported in Saudi Arabia, the UAE and Korea. The first outbreak occurred in a hospital in Jeddah, Saudi Arabia. On a mission, the WHO analyzed 128 laboratory-confirmed cases that had symptom between February 17 and April 26, 2014. An estimated 60% of all cases analyzed were reported in a hospital setting. The second hospital outbreak occurred in the UAE and resulted in a total of 28 cases in the city of Al Ain. It is unclear whether transmission occurred from the index case or from non-human sources.

The third outbreak in South Korea, which began in May 2015, is the largest nosocomial outbreak of MERS-CoV outside the Middle East. This outbreak started from a single person who travelled to four countries in the Middle East and who appears to have transmitted infection to close relatives, patients sharing the same room and health care workers providing care. These exposures happened before MERS-CoV was suspected or diagnosed. The outbreak in the Republic of Korea has been brought under control, with no new cases reported since July 4, 2015. Nosocomial and home-based transmission have been previously observed (e.g., in KSA, UAE, France, United Kingdom).

An increasing incidence of MERS-CoV from March-April suggests a seasonal pattern. The apparent seasonal increase in primary cases occurring for unknown reasons may be related to the weaning of young camels from their mothers in the spring of each year. In light of this, the WHO recommends avoiding contact with camels; not drinking raw camel milk or camel urine; and not eating meat that has not been thoroughly cooked.

The WHO provides recommendations for the general population as well as for high risk groups which include: (1) practicing general hygiene measures for those visiting places where camels are present and (2) handling with care animal products in order to avoid cross-contamination with uncooked foods. Individuals at high risk of severe disease include the following: people with diabetes, renal failure, chronic lung disease, and immunocompromised persons.

In their latest Risk assessment published on June 19, 2015 the WHO recommends enhancing prevention and control measures to prevent the spread of MERS-CoV in healthcare facilities. Additionally, WHO advises countries to be on high alert for MERS-CoV in travellers or migrant workers returning from the Middle East.

The IHR Emergency Committee concerning MERS-CoV had its 9th meeting on June 16, 2015. The consensus was that the conditions for a public health emergency of international concern (PHEIC) had not yet been met. The Committee noted that available evidence on genetic sequencing did not identify any significant changes in the viruses obtained from cases in the Republic of Korea compared to viruses from the Middle East and that there is no current evidence of sustained community transmission. The committee indicated that the overall situation and the possibility of international spread remains of concern. They indicated that increased surveillance in many countries is needed to better monitor trends related to the spread of this virus. Additional studies are required to better understand the risk factors for infection and transmission. WHO does not recommend the application of any travel or trade restrictions and considers screening at points of entry to be unnecessary at this time.

Summary of literature

A modelling study published in November 2013 has estimated that at least 62% of symptomatic cases may have gone undetected note 1. This is not unusual as many surveillance systems are often unable to capture mild and asymptomatic cases. However, there is insufficient epidemiological information to determine whether transmission is self-sustaining in humans and also, what role mildly symptomatic and asymptomatic cases play in disease transmission.

Recent studies support the idea that camels serve as a primary source of MERS-CoV in infection humans, and that other livestock are not involved. The discovery of the route of transmission between camels and humans remains critical to stopping initial introduction into human populations. The limited data available on exposures of primary cases (patients who do not appear to have contracted infection from another human) suggests that transmission is often indirect note 2. There continues to be a need for well planned, structured investigations carried out in conjunction with exposure investigations in humans.

In a study published on May 14, 2014, the U.S. Centers for Disease Control and Prevention (CDC) describes their experience with their first two MERS-CoV cases on American soil Footnote 4. Infection prevention and control methods included self-monitoring, use of mask, voluntary house quarantine and guidelines around timing for HCWs returning to work following exposure to MERS-CoV (consult article for full details). The U.S. CDC has also upgraded their travel alert to a level 2 which includes enhanced precautions when traveling to countries in or near the Arabian Peninsula and are planning to work in health care settings.

No vaccine or effective antiviral treatment is currently available for MERS-CoV. However, in an article published in mBio on September 10, 2013 researchers from the University of Madrid developed a mutant strain of the MERS-CoV virus that may be used as a basis for a safe and effective vaccine against MERS-CoV once safeguards can be engineered note 3. Additional work is still required before clinical trials can begin, as only one safeguard is currently in place and the US FDA requires at least three to ensure the virus does not revert to its virulent form.

On 8 August 2013, WHO issued an advice note (PDF Document)External Link on home care for patients infected with MERS-CoV. This was developed to meet the urgent need for recommendations on the safe home care for patients with MERS-CoV infection presenting with mild symptoms and public health measures related to management of asymptomatic contacts.

On 4 June 2015, the WHO published guidelines for Infection prevention and control during health care for probable or confirmed cases of MERS-CoV infectionExternal Link.


Footnote 1
Cauchemez S, Fraser C, Van Kerkhove MD, et al. Middle East respiratory syndrome coronavirus: quantification of the extent of the epidemic, surveillance biases, and transmissibility. Lancet Infect Dis. 2013. http://dx.doi.org/10.1016/S1473-3099(13)70304-9
Footnote 2
World Health Organization. Middle East respiratory syndrome coronavirus (MERS-CoV) Summary and literature update - as of 27 March 2014. http://www.who.int/csr/disease/coronavirus_infections/MERS_CoV_Update_27_March_2014.pdf?ua=1
Footnote 3
Almazán F, DeDiego ML, Sola I, et al. 2013. Engineering a replication-competent, propagation-defective Middle East respiratory syndrome coronavirus as a vaccine candidate. mBio 4(5):e00650-13. doi:10.1128/mBio.00650-13.
Footnote 4
Bialek SR, Allen D, et al. First Confirmed Cases of Middle East Respiratory Syndrome Coronavirus (MERS-CoV) Infection in the United States, Updated Information on the Epidemiology of MERS-CoV Infection, and Guidance for the Public, Clinicians, and Public Health Authorities-May 2014. MMWR. 2014. http://www.cdc.gov/mmwr/preview/mmwrhtml/mm63e0514a1.htm
Footnote 5
World Health Organization. World-travel advice on MERS-CoV for pilgrimages.
http://www.who.int/ith/updates/20140603/en/

Virus Characteristics

Virus isolates have been cultured and genome sequences have been made publicly available. All five of the sequenced viruses have a high degree of genetic similarity. Preliminary analyses show that the viruses are genetically somewhat similar to bat coronaviruses, but distinct from the Severe Acute Respiratory Syndrome coronavirus (SARS-CoV) which caused an international outbreak in 2003 in humans.

It should be noted, however, that the similarity does not necessarily imply that bats are the reservoir for the human virus or that direct exposure to bats or bat excreta were responsible for infection.

Recommendations for Canada

Surveillance

Health care professionals are encouraged to maintain vigilance for cases of MERS-CoV infection, and notify the appropriate Public Health Departments of any persons under investigation. The national case definition for MERS-CoV is to be used for the surveillance of MERS-CoV. For guidance on surveillance objectives and activities, please refer to the national surveillance guidelines for MERS-CoV.

Provinces and Territories are asked to report confirmed cases of MERS-CoV infection to the Public Health Agency of Canada using the Emerging Respiratory Pathogens and Severe Acute Respiratory Infection (SARI) Case Report Form.

Laboratory

Laboratory testing should be conducted in accordance with the Canadian Public Health Laboratory Network's Protocol for Microbiological Investigations of Severe Acute Respiratory Infections (SARI). Follow infection prevention and control guidelines when collecting respiratory specimens. Be aware of approaches in your jurisdiction.

Laboratory confirmation is obtained by detection of the virus using (a) MERS-CoV specific nucleic acid amplification test (NAAT) with up to two separate targets and/or sequencing; or (b) virus isolation in tissue culture note a; or (c) serology on serum tested in a WHO collaborating center with established testing methods. Initial screening tests specific for MERS-CoV can be performed in select laboratories (i.e. primarily provincial public health laboratories); however, such cases are considered probable pending NML confirmation.  Laboratories with specimens that screened positive for MERS CoV should forward these to their local public health laboratory (PHL) that can facilitate confirmatory testing at the NML.

For more detailed information, refer to the National Surveillance Guidelines for Human Infection with Middle East Respiratory Syndrome Coronavirus (MERS-CoV).

The WHO published interim recommendations for laboratory testing for MERS-CoVExternal Link. (September 2014).

Travel Health Notice

A travel health notice is posted on the Agency's website. It does not recommend any restrictions on travel but encourages travelers to take routine precautions.

Infection Control

Health care facilities are reminded of the importance of systematic implementation of infection prevention and control (IPC) measures. Health care facilities that provide care for patients suspected or confirmed with MERS-CoV infection should take appropriate measures to decrease the risk of transmission of the virus to other patients, health care workers and visitors. Recommendations for infection prevention and control measures for patients presenting with suspected or confirmed infection or co-infection with MERS-CoV in acute care settings is posted on the Agency's website. This guidance will be updated as new information becomes available.

Biosafety

MERS-CoV is classified as a Risk Group 3 human pathogen given that this virus can cause serious illness in humans, while the public health risk is low since the risk of spread of the virus in the community appears to be low. Containment Level 3 is required for all proliferative work (in vitroor in vivo), and non-proliferative diagnostic activities can be conducted at Containment Level 2 with the use of additional operational practices as outlined in Biosafety Advisory: Middle East Respiratory Syndrome Coronavirus (MERS-CoV).


note a
Virus isolation in tissue culture should be performed in a BSL3 facility only. Canada’s National Microbiology Laboratory (NML) has this capacity.