Epidemiology age distribution 3-8 weeks reported incidence 1-5 per 1,000 births highest incidence in first-born infants 4-5 times more common in boys than girls more common in western world a less common in black and asian patients than white patients in United StatesEpidemiology ◼ age distribution : 3-8 weeks ◼ reported incidence 1-5 per 1,000 births ◼ highest incidence in first-born infants ◼ 4-5 times more common in boys than girls ◼ more common in Western world ◼ less common in black and asian patients than white patients in United States