Fentanyl is 50 times stronger than heroin and 100 times more effective than morphine. The powerful opiate is causing a public health crisis in Mexico's northern neighbor.

Mexican Health authorities assure that fentanyl has not reached the national market. Expert warns that in northern Mexico 80% of the heroin samples tested contained fentanyl, so the possibility that this substance is circulating in the center of the country is “very high.“F fentanyl is dangerously close, there is a risk. If we assume that it is not there and we do not have the antidote, people are going to die,” she says.