0927 Are we underdiagnosing congenital rubella in South Africa?

In an elegant review and analysis published by Schoub et al from the National Institute for Communicable Diseases, a strong case is made for the likely underdiagnosis of the congenital rubella syndrome (CRS) in this country. Based on serology (IgG and IgM) carried out between 1998 and 2008 in 8940 patients with what they termed “rash-like illness” plus fever ± cough ± conjunctivitis ± coryza, the researchers showed that there is a significant immunity gap in women of childbearing age (15 – 49). This gap was greater in the private sector than in the public sector (10.7% vs 5.4%; p<0.0005). Statistical modeling that included the “force of infection,” (age of onset of infection, reproductive rate and level of coverage needed to achieve herd immunity) was then used to estimate CRS incidence. Results for 2005 for example suggest that some 650 cases were likely to have occurred in the country (69/100000 live births). The rates differ by province and do not take foetal loss rates into account. The authors make the point that cases may be missed at birth, present later, and not be reported to health authorities. Their concern is that current immunization policies and practices, particularly in the private sector, might be aggravating the situation: there is fair infant coverage but without a selective programme for adolescent females. Under these circumstances the susceptible age moves up and pregnant women become targets for infection, especially during epidemic years (which seem to occur in cycles, with 2009 predicted to be one). An epidemic of CRS in Greece in 1993 was attributed to this scenario with an unprecedented 24 cases per 1000 births. The proposed solution is the inclusion of MMR into the national schedule (instead of measles alone) but preceded by a robust programme for selective immunization of prepubertal/adolescent females and a strengthening of routine immunization coverage to >80% in order to reduce the levels of circulating virus.

Read more:
S Afr Med J 2009; 99: 515-9 and 483
BMJ 1999; 319: 1462-7
WHO. Rubella vaccines. Wkly Epidemiol Rev 2000; 75: 161-9