The NICD has been inundated with fever-rash samples for testing, and it is evident that there is a marked increase in rubella cases across the country. Over 8,700 IgM positive cases have been identified up until week 40. To date 98% (8543/8723) of cases have occurred in children under 15 years of age, with the bulk occurring in the 5-9-year age group.
The number of cases in 2024 is exceeding the number of rubella cases identified through fever-rash surveillance cases since 2015. The number of samples and proportion testing positive by province is shown in Table 2 (full report, link below). Delays in procurement of testing kits has led to a delay in sample testing.
Presently, an estimated 6,000 samples are awaiting testing, including samples from week 40 (commencing 29 September 2024) onward. Whilst a seasonal increase in rubella cases is expected every year, usually occurring from September to December each year, the number of cases is much larger in 2024 compared with previous years.
Reason for the Large Number of Cases in 2024
The reason for the large number of cases this year, compared with previous years, is because many children entered 2024 without prior exposure to rubella, or without being vaccinated against rubella. Three factors have led to the large number of children entering 2024 without rubella immunity – as follows:
- Immunity to rubella infection or rubella vaccination is lifelong. If children are not vaccinated against rubella, and never come into contact with rubella virus through natural infection, children will remain susceptible to rubella.
- Vaccination against rubella has not been not part of our routine EPI programme prior to 2024. The Department of Health is presently rolling out the combined measles-rubella-containing vaccine (MRCV), which will be administered to 6 and 12 months old children as soon as each province exhausts their stock of measles-containing vaccine (MCV)
- The non-pharmaceutical interventions that were applied during the SARS-CoV-2 pandemic interrupted transmission of rubella, and for the period 2020-2022 there were almost no rubella cases identified from the NDoH/NICD fever-rash surveillance (Figure 1, Table 1, full report, link below).
The above three facts mean that children who were born in the last 3-5 years and children between the age of 5-14 years who have not been infected before 2020 during seasonal rubella have had very little natural exposure to wild-type rubella virus, and have not received rubella vaccine. This has created an ‘immunity gap’ – i.e. a larger than usual number of children who are susceptible to rubella. The seasonal increase in 2024 has exposed these many susceptible children to rubella infection, and thus, there is a larger number of rubella cases than in prior years.
Clinical implications of the increase in rubella infection
Regarding clinical aspects of rubella infection, in children and adults, rubella is a self-limiting infection that presents with fever and a maculo-papular rash, myalgia, enlarged lymph nodes, headache and conjunctivitis. Occasionally, persons may develop joint pain (arthralgia), low platelets and a mild encephalitis. The complications are usually self-limited. Very rarely, cases of Guillian-Barre syndrome have been reported after rubella infection. Rubella is of concern because of the risk of rubella infection in women of child-bearing age during the first trimester of pregnancy.
However, rubella infection carries a risk of congenital rubella syndrome. Women who are pregnant in their first trimester and acquire rubella may pass the infection onto their fetus, who may develop congenital rubella syndrome (CRS).
Clinicians who suspect congenital rubella infection may submit blood and nasopharyngeal swabs to the NICD for testing. The specimen should be marked ‘Priority sample, URGENT testing required’, and an email should be sent to the named individuals above. All cases of CRS should be notified to the NICD using the NMC notification forms found at NMC.
For more information about rubella, click here.
