Assessing bacterial contamination in environmental samples is critical in determining threats to public health. The classical methods are time-consuming and only recognize species that grow easily on culture media. Viable but non-culturable (VBNC) bacteria are a possible threat that may resuscitate and cause infections. Recent dye-based screening techniques employ nucleic acid dyes such as ethidium monoazide (EMA) and propidium monoazide (PMA), along with many fluorescent dyes, which are an effective alternative for viability assessment. The measurement of cellular metabolism, heat flow and ATP production has also been widely applied in detection approaches. In addition, RNA-based detection methods, including nucleic acid sequence-based amplification (NASBA), have been applied for bacterial pathogen determination. Stable isotope probing using 13C, 15N and 18O, which are mobilized by microbes, can also be used for effective viability assessment. Future detection tools, such as microarrays, BioNEMS and BioMEMS, which are currently being validated, might offer better microbial viability detection. © 2019 The Authors. All rights reserved.