Issued by the National Institute for Communicable Diseases based on laboratory testing data
Highlights
- The NICD has tested 5853 serum samples for measles since epidemiological week 40, 2022, of which 976 (17%) were confirmed positive. In outbreak-affected provinces, 970 cases have been reported since week 40, 2022. In the past week (week 16 up until week 17, 24/04/2023) there have been 8 laboratory-confirmed measles cases detected across the country, of which the majority were from Limpopo (5).
- The percentage of samples testing positive (PTP) decreased from 20% of 83 samples tested in week 15 to 14% of 53 samples tested in week 16.
- The measles strain detected in Limpopo province and North West province is genotype D8 which is similar to the strain in Zimbabwe in the 2022 outbreak.
- In the provinces where an outbreak has been declared, the most affected age groups are still the 5-9-year-olds (43%) with a considerable proportion of cases reported among the 1-4 (24%) and 10-14 age groups (20%).
- The majority of cases (67%) were reported from primary healthcare facilities, and the highest proportion of cases reported from hospitals (59%) was reported in children under the age of one.
- Nationally, the reproduction number as of 2023-04-18 was estimated to be 0.55 (0.25 – 1), suggesting that infection incidence is likely decreasing. There is a 94% chance that the reproduction number was below 1 as of 2023-04-18.
- At the provincial level, the reproduction number as of 2023-04-18 was estimated to be 0.73 (0.43 – 0.96) in Limpopo, 0.48 (0.25 – 0.94) in Mpumalanga, 0.66 (0.46 – 0.91) in Gauteng, and 0.42 (0.23 – 0.64) in North West, suggesting that infection incidence is decreasing.
- Note that April 2023 included two major holiday weekends in South Africa (the Easter holidays from 2023-04-07 to 2023-04-10 and Freedom Day / Workers’ Day from 2023-04-27 to 2023-05-01). During this time, it is especially important to monitor other indicators, such as the percentage testing positive, for consistency with reproduction number estimates when interpreting trends.
Outbreak overview
From epidemiological week 40, 2022 (ending 8 October 2022) to week 17, 2023 the NICD has tested 5853 serum samples for measles of which 976 (16.67%) were confirmed measles cases. The number of samples submitted and the percentage of laboratory-confirmed measles-positive cases are shown in Figure 1. From epidemiological week 40 of 2022 to week 17 of 2023, 970 laboratory-confirmed cases were reported from eight provinces with declared measles outbreaks; Limpopo (410 cases), Mpumalanga (108 cases), North West (216 cases), Gauteng (166 cases), Free State (29 cases), Western Cape (14), KwaZulu-Natal (20) and Northern Cape (7) (Table 1). The geographical distribution of cases across South Africa from week 40 of 2022 until week 17 of 2023 is shown in Figure 2The number of blood samples and throat swabs submitted to the NICD for measles serology and PCR testing has decreased from 83 in week 15 compared to 57 in week 16 (Figure 3).
Figure 1. Number of serum samples submitted to the NICD for measles, week 40 2022, until week 17, 2023, and the number (dark green) and % tested positive (red line), by epidemiological week using the date the specimen was collected. *Data from week 18 will be updated in next week’s situation report, when complete data from samples collected that week becomes available
Figure 2. Distribution of laboratory-confirmed measles cases by testing site (red dots – the size of the dot indicates the number of cases from that facility) and district of South Africa (deepening colour of blue indicates the total number of cases by sub-district), from week 40 to week 18, 2023.
Figure 3. Number measles of tests conducted from week 40 2022, until week 18, 2023, by province and epidemiological week using the date the specimen was collected. *Data from week 18 represent partial data, and will be updated in next week’s situation report, when complete data from samples collected that week becomes available.
