Harm reduction: closing the distance.
D000293:Adolescent; D000328:Adult; D002170:Canada / Q000453:epidemiology; D015658:HIV Infections / Q000209:etiology* / Q000517:prevention & control; D006526:Hepatitis C / Q000209:etiology* / Q000517:prevention & control; D006801:Humans; D008875:Middle Aged; D011314:Preventive Health Services / Q000458:organization & administration*; D015819:Substance Abuse, Intravenous / Q000150:complications* / Q000453:epidemiology