Thursday, October 30, 2014

Comparison of WHO and ECDC MERS case counts

As of October 16, 2014, the World Health Organization (WHO) reported a total of 877 cases of Middle East respiratory virus syndrome (MERS) from WHO member states (through October 11, 2014 link).  The European Centre for Disease Prevention and Control (ECDC),  a European disease monitoring organization established in 2005 (link), has reported a total of 906 MERS cases from around the world through October 21, 2014 (link). Both WHO and ECDC provide updates on the MERS outbreak, however neither these agencies provides a publicly available line list of cases.

Because it appears that the next MERS wave has started on the greater Arabian Peninsula in the Middle East, is worth discussing the apparent discrepancy in the number of MERS cases between the WHO and the ECDC.  

The table below compares the current counts of MERS cases for WHO and the ECDC through specific dates.  The differences in the case counts are discussed below by country.  WHO and the ECDC enumerate cases based on the reporting country (under IHR), rather than the source country of infection.  Also included in the table below is a column with the case counts that have been tabulated by (link). The FluTrackers’ case counts are not directly comparable to the WHO or ECDC data because the FluTrackers’ counts are based on the country of the source of infection not the reporting country.

There are minor discrepancies between the WHO case counts and the ECDC case counts as noted in the detailed discussions below. It would be beneficial if both of these organizations would make their line list of cases publicly available on the internet.

Discussion of table discrepancies between WHO and ECDC


The case count noted by WHO for Jordan does not appear to include the seven retrospectively confirmed cases from the first MERS cluster in Jordan in 2012 (link).


The WHO does not recognize any cases from the Philippines. At least two possible MERS cases have been reported from the Philippines. The first was a male nurse who tested positive for MERS in United Arab Emirates and later tested negative in the Philippines in April, 2014 (link). The second was a female nurse who was tested in Saudi Arabia and arrived in the Philippines after the positive test results were announced by Saudi Arabia (link). It is not clear which case, if either, of these two cases is included as a case from the Philippines by the ECDC.


On October 12, 2014, the Supreme Health Council of Qatar officially announced the first MERS case in Qatar in 2014 (link), so  the WHO may report his case in the future.

Saudi Arabia

As of October 21, 2014 the Saudi Arabia Ministry of Health web page reports a total of 771 MERS cases. The ECDC count for MERS cases from Saudi Arabia is 771, matching the Saudi Arabia Ministry of Health total.

The last official WHO update prior to October 21, 2014 was published on October 16, 2014 (link). At that time, the WHO case count for Saudi Arabia was apparently 756. There is a disparity of 15 MERS  cases between the WHO case count and the ECDC case count for Saudi Arabia. This difference appears to be a function of differential reporting dates rather than major disparities in the case counts. Between  October 11 and October  21, the Saudi Arabia Ministry of Health reported a total of 12 MERS cases that will probably be reported and incorporated in the WHO count in the near future.  

This would bring the WHO total through October 21 to 768.

The reason for the difference of three cases between the WHO data and the ECDC data is uncertain. Any number of additions and deletions (due to duplicates and false positives) in the case counts could affect this differential in the case counts.


The first MERS case in Turkey was only reported on October 17, 2014 (link). The WHO later reported this case on October 24, 2014 (link).

United Arab Emirates

It is not clear how the ECDC determined an additional four cases from United Arab Emirates compared to the WHO counts.


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