Review of immunological and virological aspects as contributory factors in Sudden Unexpected Death in Infancy (SUDI)

• SUDI remains one of the major contributors to infant mortality worldwide.
• Viral and bacterial infections are often implicated in these cases.
• Histology and laboratory results must agree for a diagnosis of infection.
• Different investigation protocols limit comparison of results worldwide.
• Bigger studies, sampling of more organs and updating protocols are crucial.

Currently in South Africa research into sudden unexpected death in infancy (SUDI) is limited. The causes of sudden infant death syndrome (SIDS) remain obscure despite full medico-legal investigations inclusive of autopsy, scene visit and ancillary studies. Viral infections play an important role as a multitude of respiratory viruses have been detected in autopsy specimens and are implicated in these deaths. The specific contribution of viruses in the events preceding SIDS still warrants deciphering. Infancy is characterised by marked vulnerability to infections due to immaturities of the immune system that may only resolve by the age of 24 months. Routine viral screening of all SUDI cases at Tygerberg Forensic Pathology Service (FPS) Mortuary in Cape Town focuses on only a portion of respiratory viruses from lung and liver tissue. This review highlights important virological and immunological aspects regarding investigations into the infectious nature of SUDI, including the lack of national standardised guidelines for appropriate specimen collection at autopsy and subsequent laboratory analysis.