The quality of reporting has allowed almost real-time insight into the dynamics of the outbreak. Aggressive contact tracing and testing for infection may help explain the rapid expansion of the outbreak. Human-to-human transmission has been documented. At this stage, WHO has no evidence of sustained transmission in the community.
The Republic of Korea’s first, or “index”, case was confirmed on 20 May and notified to WHO the same day. The case occurred in a 68-year-old national of the Republic of Korea with a recent history of travel to 4 countries in the Middle East. The case was asymptomatic during his return flight to Republic of Korea on 4 May.
He developed symptoms on 11 May and subsequently sought care at 2 out-patient clinics and 2 hospitals, creating multiple opportunities for exposure among health care workers and other patients.
As the index case provided no history of potential exposure to the virus, MERS-CoV was not suspected and the patient was not treated in isolation. Efforts are under way to gather more information about exposures during the patient’s travels in the Middle East.
Expansion of the outbreak
The outbreak is the largest reported outside the Kingdom of Saudi Arabia, where the disease first emerged in April 2012 and the vast majority of cases have occurred.
To date, contact tracing has identified a total of 25 laboratory-confirmed cases, including the index case and among health care workers caring for him, patients who were being cared for at the same clinics or hospitals, and family members and visitors.
Some of these additional cases were in the same room as the index case; others were on the same ward. Though data are preliminary, exposure times that led to infection may have been as short as 5 minutes to a few hours.
To date, 2 of these cases have been fatal.
Given the number of clinics and hospitals that cared for the index case, further cases can be expected.
On 26 May, 1 of the confirmed cases with an exposure history in Republic of Korea travelled, against medical advice, to Guangdong, China, via Hong Kong (SAR). He was symptomatic at the time of travel. On 29 May, China informed WHO that the patient, who was isolated at a Huizhou hospital, tested positive for the MERS coronavirus.
The occurrence of such a large outbreak outside the Middle East is a new development, as is exportation of the disease to a third country. The Ministry of Health has further reported that 2 recently confirmed cases represent a third generation of transmission – from the index case, to someone exposed to that case, to a third person with no direct exposure to the index case.
Consistent application of adequate measures for infection prevention and control has halted other large clusters of cases associated with health care facilities. WHO recommends that droplet precautions be added to standard measures when providing care to patients with symptoms of acute respiratory infections.
WHO does not advise special screening at points of entry nor does it currently recommend the application of any travel or trade restrictions.
MERS-CoV is a newly emerging disease that remains poorly understood. Much about the behaviour of the virus remains shrouded in scientific uncertainty, though evidence is mounting that dromedary camels can transmit the virus to humans through close contact.
WHO is confident that investigations under way in Republic of Korea, including the sequencing of viruses and sharing of the findings, will contribute to further scientific understanding of this disease.