The number of Middle East Respiratory Syndrome, or MERS cases in South Korea has grown to 30 after The Korean Health & Human Welfare reported the confirmation of five additional cases (computer translated).

Middle East Respiratory Syndrome Coronavirus
Middle East Respiratory Syndrome Coronavirus /National Institute of Allergy and Infectious Diseases (NIAID

In addition, the World Health Organization (WHO) issued a situation assessment yesterday on MERS in the Republic of Korea. Here are some excerpts:

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 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 (reported before the latest Korea HHW update above), 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.

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.

WHO is confident that investigations under way in Korea, including the sequencing of viruses and sharing of the findings, will contribute to further scientific understanding of this disease.