Diagnostic options for investigating viral respiratory pathogens in sudden unexpected death in infancy (SUDI) cases

Abstract

Sudden and unexpected deaths in infants have occurred for centuries. It has generally been referred to as sudden infant death syndrome (SIDS). A new concept, called sudden unexpected death in infancy (SUDI) was introduced in 1989, which is used for all unexpected deaths in infants and babies, usually during sleep, where fatal injury can be excluded. By definition, cases that remain unexplained after thorough investigation are still classified as SIDS. Many risk factors have been associated with SUDI, e.g. poor socioeconomic conditions and prenatal care, multiple pregnancies, parental drug use and smoking, gender, low birth weight, recent infection and the sleeping environment. Ultimately, SUDI is most probably a result of a combination of predisposing factors, external stresses and underlying vulnerabilities, although the exact mechanism of death remains unknown. Viral infections are common in infants and have repeatedly been implicated in SUDI. Respiratory infections occur frequently in infancy and early childhood and inflammatory changes in the respiratory tract in SUDI cases is often found. Different diagnostic approaches for investigating respiratory viruses in SUDI cases have been reported in the literature, but in the absence of standardised SUDI investigation protocols, research from different centres cannot be compared. Viral viability is compromised in post-mortem samples and results should be interpreted with care, as the mere presence of a pathogen does not confirm that to be the cause of death. It is therefore imperative to use a combination of diagnostic approaches in parallel with epidemiological and clinical information in SUDI cases.