Surveillance and Testing for Middle East Respiratory Syndrome Coronavirus, Saudi Arabia, March 2016–March 2019

During March 2016–March 2019, a total of 200,936 suspected cases of Middle East respiratory syndrome coronavirus infection were identified in Saudi Arabia; infections were confirmed in 698 cases (0.3% [0.7/100,000 population per year]). Continued surveillance is necessary for early case detection and timely infection control response.

Each surveillance year, an average of 66,979 (range 60,659-77,886) suspected case-patients were tested for MERS-CoV. On average, 5,431 (range 2,836-9,154) suspected case-patients were tested monthly during the study period ( Figure). The average monthly number of suspected case-patients tested did not change 1572 Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 26, No. 7, July 2020  Annually, 203.0 suspected case-patients/100,000 population were tested for MERS-CoV, and 0.7/ 100,000 population were positive (Table 3). Testing and positivity rates did not vary substantially from year to year (Appendix Table 1, https://wwwnc.cdc. gov/EID/article/26/7/20-0437-App1.xlsx). Riyadh HAD had the highest annual testing rate (328.0 suspected cases/100,000 per year). The highest positivity rate per population was in Jouf HAD (2.5 confirmed cases/100,000 population per year) and was largely attributable to an August 2017 outbreak. The study period encompassed 3 Hajj pilgrimage seasons; during these periods, 2,738 pilgrims were tested for MERS-CoV, none of whom tested positive.
For 82.2% of persons with suspected MERS-CoV infection, a reason for testing was reported (Appendix Table 2). Most were tested because they had signs of pneumonia or acute respiratory distress syndrome (69.9%). Testing because of an epidemiologic link accounted for the highest proportion of positive results overall (0.8%). A higher proportion were tested because of an epidemiologic link after the definition change (19.5%) than before (7.5%).

Conclusions
Saudi Arabia continues to perform extensive surveillance and testing for MERS-CoV. During the 3-year study period, the MoH tested >65,000 suspected MERS-CoV case-patients per year on average. Of these, 0.3% were positive for MERS-CoV, representing 0.7 confirmed cases/100,000 population per year. As a robust, national surveillance system, HESN enables the geographic and temporal monitoring of trends in testing and surveillance. Compared with HESN MERS-CoV surveillance data from 2015-2016, the percentage of suspected case-patients testing positive (0.7%) and the rate of confirmed cases (1.2/100,000 population) decreased (8). Peaks in percentage positivity corresponded to documented MERS-CoV outbreaks (9-11). The few large recent outbreaks and the reduction in cases might be indicative of robust testing and contact-tracing efforts and early intervention for healthcare infection control.
During the study period, the case definition for suspected cases was revised with the goal of maintaining the sensitivity of the case definition while increasing specificity. Based on limited data (7 complete months of data postrevision), the average number of monthly tests remained constant before and after this change. The change in the case definition is reflected in the reasons for testing persons with suspected MERS-CoV infection. A comparison of the reasons for testing before and after the change found that most persons were tested because they had signs of pneumonia or acute respiratory distress syndrome. Unsurprisingly, in both periods, the highest percentage positive was among those with an epidemiologic link to a MERS-CoV patient or exposure to dromedaries. Comparing data from before and after the case definition change, however, was limited by the relatively short period examined after the definition change and a high percentage of missing data, particularly during implementation of the revised case definition. Although the case definition change took effect in April 2018, HESN was not updated to reflect the change until July 2018. This lag might have affected reporting, and actual implementation of the case definition change likely varied by site. In addition, completeness of the data varied and was likely influenced by differential reporting practices, which affected the availability of data for analysis. Targeted efforts continue to improve the accuracy and completeness of reporting. Additional analysis using more complete data over a longer period would be informative to determine whether the revised case definition might result in changes in testing practices.
Surveillance for MERS-CoV in Saudi Arabia captures and provides important information on suspected and confirmed cases and trends in testing. Continued robust MERS-CoV surveillance is pivotal for the early ascertainment of cases and the effective implementation of control measures.

About the Author
Dr. Abdullah Alzahrani is the general supervisor of the Health Electronic Surveillance Network, Ministry of Health, Saudi Arabia. His primary research interests include public health surveillance for infectious diseases.