Genotypic analysis of rhinovirus and human respiratory syncytial virus in sudden unexpected death in infancy cases at Tygerberg Hospital, Cape Town, South Africa.

Infant mortality remains a major global concern. Sudden unexpected death in infancy (SUDI) is reported globally and an infant mortality rate of 23.129 per 1 000 live births has been reported in the Western Cape, South Africa, in 2024. Infections are often confirmed in SUDI cases admitted to the Tygerberg Medico-legal Mortuary in Cape Town, but molecular diversity in respiratory viruses is underreported. A total of 162 previously confirmed polymerase chain reaction (PCR)-positive trachea and / or lung samples from SUDI cases collected between 2015 and 2019 were retested for either rhinovirus or human respiratory syncytial virus (RSV). Sixty-four samples were positive for rhinovirus and 15 for RSV. Results from 5 of all positive samples were outside the PCR assay amplification limits determined by the cycle threshold (Ct) value and were excluded. Another 4 samples did not amplify, and the remaining 70 underwent subsequent sequencing, but successful sequences could only be obtained in 53 samples. All three rhinovirus (A, B and C) genotypes were identified, with RV-A most prevalent, followed by RV-C and RV-B. RSV-A and RSV-B were detected equally, and after amino acid alignment, 20 amino acid duplication and nine substitutions were found that confirmed two RSV-BA9 genotypes. This study describes the molecular and phylogenetic characterisation of specific respiratory viruses in SUDI cases in South Africa. However, the rapid decline in viral viability in post-mortem samples does not allow correlation between viral genotypes and cause of death or disease severity. Future prospective studies should therefore investigate temporality and associations between specific viral strains and clinical disease severity and mortality.