Clinical criteria

• Born at term (gestational age >/= 37 weeks) with uncomplicated nursery stay
• Previously healthy infants
• No toxic manifestations
• No focal bacterial infection (except otitis media)

Laboratory criteria

• White blood cell count 5-15 x 10⁹/l, < 1.5 x 10⁹ band cells/l, or band/neutrophil ratio < 2
• Normal urine analysis results (negative Gram stain of unspun urine, negative leucocyte esterase and nitrite, fewer than five white blood cells per high power field)
• When diarrhoea is present, no haem and fewer than five white blood cells per high power field
• Fewer than 8 x 10⁶ white blood cells/l in cerebrospinal fluid, if lumbar puncture is performed, and negative Gram stain findings in cerebrospinal fluid
• No infiltrate on chest radiograph