Limited information is available on etiology of serious bacterial infections in community settings. Hospital-based studies suggest that most infections in the first week of life are due to Gram-negative pathogens, and many may be environmentally rather than maternally-acquired, owing to unhygienic delivery practices. Such practices may also explain the predominance of Gram-negative infections among home-born infants, although data from home settings are limited. These findings have implications for developing prevention and management strategies in communities and hospitals.