Middle East Respiratory Syndrome (MERS) in the Republic of Korea

On 13 June, WHO and the Republic of Korea’s Ministry of Public Health and Welfare presented the results of their joint assessment of the MERS outbreak. The assessment led to a series of recommendations. These include further strengthening of measures to control the current outbreak, such as continuing to strengthen contact tracing, and enhanced precautions in hospitals to prevent transmission, as well as increased communication with the public and better preparation for future outbreaks.

Current situation

As of 15 June 2015, the Republic of Korea has reported 150 laboratory-confirmed cases and 15 deaths. The outbreak, which started with the introduction of MERS-CoV infection into the country by a single infected traveler, was amplified by infection in hospitals and movement of cases within and among hospitals.

The number of new cases occurring each day, which is the most accurate picture of whether the outbreak is slowing down, appears to be declining. This suggests that the containment measures in place are having an effect in reducing new infections. As these containment measures have been recently intensified, it is too early to measure their full impact on the transmission.

An early concern was whether the MERS-CoV virus changed and whether the transmission patterns in Korea were different compared with past outbreaks occurring in the Middle East. Scientists in the Republic of Korea and China have completed full genome sequencing of coronaviruses from the current outbreak. Findings were analyzed by a group of virologists convened by WHO. Preliminary analysis of these findings suggest that the MERS CoV viruses isolated in Korea are similar to those isolated in the Middle East. Furthermore, the joint mission found that the transmission patterns are similar to that seen previously in the Middle East.

Challenges in early diagnosis

MERS CoV is difficult to diagnose, particularly in the early part of an outbreak when awareness is relatively low. The initial, or “index” case, did not report his recent travel history to the Middle East when he first sought treatment. MERS was not suspected, and the initial case exposed others for more than a week before he was isolated. Additionally early symptoms of MERS resemble other influenza-like illnesses making it difficult to recognize or suspect MERS.

In the early stage of the disease when upper respiratory track is infected, the virus may be more difficult to detect. The laboratory diagnosis is more robust with samples taken in the lower respiratory track usually in the later stage of the disease when the patient is hopitalised. Furthermore, samples taken from the upper respiratory system (e.g., nasal swabs) can sometimes provide negative test results when lower respiratory samples, which are difficult to collect, may be positive.

As noted by the joint mission, Korea follows a policy of retesting symptomatic contacts following initial negative results.

As has been seen in this and other outbreaks, lapses in early detection and isolation, and the tendency to refer patients to other facilities for testing or management, can facilitate rapid spread from a single infected person.

MERS CoV spread in Korea

Conditions and cultural traditions specific to Korea have likely also played a role in the outbreak’s rapid spread. The accessibility and affordability of health care in Korea encourage “doctor shopping”; patients frequently consult specialists in several facilities before deciding on a first-choice facility.

Moreover, it is customary in Korea for many family members and friends to visit loved ones when they are in the emergency room or admitted to hospital. It is also customary for family members to provide almost constant bedside care often staying in the hospital room overnight, increasing the risk of close exposures in the health care setting.

Actions to control the MERS CoV outbreak

WHO and the Republic of Korea carried out a joint mission to assess the epidemiological patterns of MERS CoV in the Republic of Korea as well as the characteristics of the virus and clinical features. It also reviewed the public health measures implemented since the start identification of the first case on 20 May 2015.

The joint mission presented its findings on 13 June to the Government of Korea and publically at a press conference, at the end of their mission in the Republic of Korea. Its recommendations can be grouped into three main areas for action.

Actions to halt further spread of the virus: These recommendations include early and complete identification and investigation of all contacts; robust quarantine/isolation and monitoring of all contacts and suspected cases; full implementation of infection prevention and control measures; and prevention of travel, especially internationally, of infected persons and contacts. Furthermore, the Mission recommended that selected hospitals should be designated for safe triage and assessment of suspected MERS cases. This will help protect health care workers, while also minimizing the potential disruption of regular service delivery due to potential public reticence to seek help in facilities treating MERS patients.

Regular provision of information to the public: To ensure the public is fully informed of developments in the outbreak, the Mission recommended that regular information should be provided in both Korean and English. This should include information on the evolution of the outbreak, as well as measures to be taken or avoided. Channels most likely to be seen by the population, such as television and social media should be used for maximum reach. Local government must be fully engaged and mobilized in the national fight against this large and complex outbreak.

Preparation for future outbreaks: The Mission recommended that the Republic of Korea should strengthen the medical facilities needed to deal with serious infectious diseases, including increased numbers of negative-pressure isolation rooms; consider how to reduce the practice of “doctor shopping”; train more infection prevention and control specialists, infectious disease experts, laboratory scientists, epidemiologists, and risk communication experts; and invest in strengthening public health capacities and leadership. This outbreak also provides an opportunity for comprehensive research studies designed to close critical gaps in knowledge such as sero-epidemiological studies.

This Mission was presented with several investigations underway to evaluate transmission of MERS-CoV in health care settings, particularly in two of the hospitals associated with the most cases. As this work is still under way, the Mission members were not been able to determine what role, of any, environmental contamination, inadequate ventilation or other factors had a role in transmission of the virus in this outbreak. There is an urgent need for further investigation into these issues

Future evolution of the outbreak

All cases detected to date appear to be linked back to the index case, who was diagnosed and isolated on 20 May. To date, spread has largely occurred in the confined setting of health care facilities, with no known spillover into the general population. Korean health officials are actively monitoring a large number of close and casual contacts and it is possible, and even likely, that more cases will be reported before this outbreak is over.

In the unlikely event that cases begin increasing at a faster pace, Korea has sufficient capacity to cope, given its high awareness for suspect cases, rapid system in place to quickly isolate suspect cases, an adequate number of isolation beds, stockpiles of personal protective equipment, and testing facilities that extend to the provincial level.

WHO is encouraging Korean officials to reopen schools that were closed due to fears around MERS CoV. Schools have not been linked to transmission of MERS CoV in the Republic of Korea or elsewhere. Reopening, combined with clear messages for the public on why, could start to build confidence and trust with the population in Korea. Regular communications on the evolution of the outbreak will also build confidence both in Korea and internationally.

The mission concluded that while the outbreak that began last month has been large and complex, it is showing a similar epidemiological pattern to previous hospital-associated MERS CoV outbreaks in the Middle East, which have been fully controlled by strong basic public health measures such as infection prevention and control and early detection and isolation of cases. However, the size and complexity of the outbreak means it will be a number of weeks before the true impact of the stronger disease control measures will be seen.

WHO action

WHO will continue to actively support the Republic of Korea’s Ministry of Health and Welfare as it continues to work to bring this outbreak to an end. This includes providing updated information and conducting risk assessments and joint investigations such as the one just completed. The WHO Director-General will convene a meeting of an IHR Emergency Committee to provide further expert guidance on MERS CoV.

All outbreaks are unpredictable. This is especially true for a comparatively new disease like MERS, where so much about its epidemiology, modes of transmission, natural history, and clinical features remains poorly understood.