South African Measles Outbreak Update 2023 ( 31 March )

Highlights

  • The NICD has tested 5335 serum samples for measles since epidemiological week 40, 2022, of which 865 (16%) were confirmed positive. In outbreak-affected provinces, 859 cases have been reported since week 40, 2022. In the past weeks (week 11 up until week 12, 25/03/2023) 40 laboratory-confirmed measles cases were detected across the country, all of which were from the outbreak-affected provinces.
  • The percentage of samples testing positive (PTP) decreased from 22% of 255 samples tested in week 10 to 14% of 214 samples in week 11.
  • Measles outbreak has been declared in all the provinces in South Africa except for the Eastern Cape. In week 11, no new cases were reported in Mpumalanga, Northern Cape and Western Cape provinces.
  • The measles strain detected in Limpopo province and North West province is genotype D8, 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 (19%). Vaccination campaigns should therefore also include children aged 10 to 14.
  • The majority of cases (68%) were reported from primary healthcare facilities, and the highest proportion of cases reported from hospitals (55%) was reported in children under the age of one.
  • Members of the public are urged to ensure their children are vaccinated against measles.
  • Nationally, the reproduction number as of 2023-03-15 was estimated to be 0.74 (0.32 – 1.4), suggesting that infection incidence is likely decreasing. There is an 80% chance that the reproduction number was below 1 as of 2023-03-15.
  • At the provincial level, the reproduction number as of 2023-03-15 was estimated to be 1.2 (0.85 – 1.5) in Limpopo and 1.1 (0.74 – 1.5) in Gauteng, suggesting that infection incidence is likely increasing. Increases in Limpopo are driven by Greater Sekhukhune and Waterberg; increases in Gauteng are driven by Ekurhuleni Metro. In contrast, the reproduction number as of 2023-03-15 was estimated to be 0.72 (0.47 – 1.1) in Mpumalanga and 0.84 (0.58 – 1.1) in North West, suggesting that infection incidence is likely decreasing.

Outbreak overview

From epidemiological week 40, 2022 (ending 8 October 2022) to week 12, 2023 (ending 25 March 2023) the NICD has tested 5335 serum samples for measles of which 865 (16%) were confirmed measles cases. The number of samples submitted, and the percentage laboratory-confirmed measles positive cases are shown in Figure 1.  From epidemiological week 40 of 2022 to week 12 of 2023, 859 laboratory-confirmed cases were reported from eight provinces with declared measles outbreaks; Limpopo (329 cases), Mpumalanga (106 cases), North West (212 cases), Gauteng (146 cases), Free State (30 cases), Western Cape (11), KwaZulu-Natal (18) and Northern Cape (7) (Table 1). The geographical distribution of cases across South Africa from week 40 of 2022 until week 12 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 compared to previous weeks (Figure 3).

Figure 1. The number of serum samples submitted to the NICD for measles, week 40 2022, until week 12, 2023, and the number (dark green) and % tested positive (red line), by epidemiological week using the date the specimen was collected. *Data from week 12 represent partial data and 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 the 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 12, 2023.

Table 1. Cases of laboratory-confirmed measles tested by the NICD from all provinces in South Africa from epidemiological week 40, 2022 to week 12, 2023. Outbreak-associated cases are contained within the red bordered cells* (EC=Eastern Cape; FS=Free State; GP=Gauteng; KZN=KwaZulu-Natal; LP=Limpopo; MP=Mpumalanga NW=North West; NC=Northern Cape). * A measles outbreak is classified as three or more confirmed laboratory measles cases reported within 30 days of onset of disease, in a district. *Data from week 12 represent partial data, and will be updated in next week’s situation report, when complete data from samples collected that week becomes available.

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