Use of alcohol, tobacco, and other drugs has long been associated, both in the US and internationally, with public health problems such as chronic lung and liver disease as well as increased risk for sexually transmitted or blood-borne infections. More recently, the opioid crisis in the US has claimed more lives annually than for motor vehicle accidents. The availability of illicitly produced synthetic opioids has increased dramatically since 2013, further contributing to the public health crisis. Research in the Department of the Epidemiology of Microbial Diseases includes epidemiological and geospatial analyses of opioid-involved fatalities in Connecticut and assessing the potential public health benefits of expanded access to naloxone and expedited referral to medication assisted treatment through harm reduction organizations and emergency departments. Other studies have sought to understand the contextual factors that may contribute to risk of non-fatal opioid overdoses and whether mHealth applications can be effective tools for treating tobacco and substance use disorders.