OPRM1 and hepatitis C virus infection: With respect to hepatitis C, the risk for mother-to-child transmission is very low (<5%), making it unlikely to alter brain FC in the POE infants.105,106 However, both morphine and nicotine are considered narcotic drugs, as they both activate the mu opioid receptor at some stage,107 meaning that the observed differences in functional activity in infants with POE may not be specific to opiates.