A review of methods for the evaluation of handwashing efficacy

•Handwashing (HW) is a primary means to prevent disease transmission.•Few standard methods exist for evaluation of HW agents.•There is a need to develop standard inoculation and microbial recovery methods in HW studies.•Minimum requirements for reporting HW methods and results should be formed.

Handwashing is relied upon in numerous fields as a primary means to prevent transmission of harmful pathogens. While handwashing is a key step in disease prevention, the factors controlling its effectiveness are not always well understood, and there are extensive variations in the methodology used to assess each of these factors. This review summarizes the various factors that can impact handwashing effectiveness as well as the methods and results of studies evaluating each of these factors related to handwashing. Numerous methods are available to inoculate hands as well as to recover microorganisms from hands, and for a given method, experimental variables can be changed between researchers. These variations amongst methods as well as variations in reporting experimental results can make it difficult to compare studies as well as challenging to accurately interpret the results between studies. Standardization of methods and reporting requirements are necessary to allow for comparison of studies so that more accurate conclusions about the handwashing process can be made. Therefore, the need for 1) the development of more standardized handwashing test methods and 2) the formation of guidelines on the minimal information required for publication of handwashing experiments are considered and discussed.