BackgroundRotavirus is the most common cause of severe gastroenteritis in children under the age of 5 years worldwide. It is well recognised that rotavirus can cause signs and symptoms beyond the gastrointestinal tract, including neurological manifestations such as encephalopathy. Mild encephalopathy with a reversible splenial lesion (MERS) is a clinico-radiological syndrome that has been associated with rotavirus. We report a case of a 4-year-old boy with clinically mild encephalopathy, who had an isolated splenial lesion in the corpus callosum on neuroimaging, and rotavirus RNA detected in faeces. We use this case as an opportunity to review the literature on rotavirus-associated MERS.Case presentationA previously healthy 4-year-old boy presented with a 2-day history of vomiting, diarrhoea, and fever, complicated by reduced level of consciousness. Magnetic resonance imaging of the brain showed a marked hyperintensity in the splenium of the corpus callosum on T2 and diffusion-weighted images. Rotavirus genome was detected by polymerase chain reaction in a stool specimen, but not in the cerebrospinal fluid. The genotype was identified as G1P8. His clinical condition improved with gradual resolution of his symptoms. No neurological complications were evident upon discharge and the patient had no recurring symptoms or significant residual defects when followed up 2 months later.ConclusionMERS is a novel clinic-radiological syndrome first described in Japan. A transient splenial lesion with reduced diffusion that appears as a high signal intensity in diffusion-weighted MRI is the main diagnostic feature. Rotavirus is one of the most common agents associated with MERS, although to our knowledge only one previous case has been reported from Europe. The majority of patients appear to achieve full recovery following rotavirus-associated MERS, irrespective of treatment. This case, together with other published reports, supports the hypothesis that rotavirus-associated MERS is unlikely to be the result of direct viral invasion of the CNS. It has been suggested that MERS may be caused by intra-myelinic axonal oedema or local inflammatory cell infiltration; however, the pathogenesis remains incompletely understood.

Group B Streptococcus (GBS) is a common intestinal colonizer during the neonatal period, but also may cause late-onset sepsis or meningitis in up to 0.5% of otherwise healthy colonized infants after day 3 of life. Transmission routes and risk factors of this late-onset form of invasive GBS disease (iGBS) are not fully understood. Cases of iGBS with recurrence (n=25) and those occurring in parallel in twins/triplets (n=32) from the UK and Ireland (national surveillance study 2014/15) and from Germany and Switzerland (retrospective case collection) were analyzed to unravel shared (in affected multiples) or fixed (in recurrent disease) risk factors for GBS disease. The risk of iGBS among infants from multiple births was high (17%), if one infant had already developed GBS disease. The interval of onset of iGBS between siblings was 4.5 days and in recurrent cases 12.5 days. Disturbances of the individual microbiome, including persistence of infectious foci are suggested e.g. by high usage of perinatal antibiotics in mothers of affected multiples, and by the association of an increased risk of recurrence with a short term of antibiotics [aOR 4.2 (1.3-14.2), P=0.02]. Identical GBS serotypes in both recurrent infections and concurrently infected multiples might indicate a failed microbiome integration of GBS strains that are generally regarded as commensals in healthy infants. The dynamics of recurrent GBS infections or concurrent infections in multiples suggest individual patterns of exposure and fluctuations in host immunity, causing failure of natural niche occupation.