Evidence-based recommendations for shower-out practices: assessing virus removal from hair using a surrogate...

This study aims to assess the risk of fomite transmission of non-enveloped viruses from different hairstyles and hair types by evaluating shower-out practices used at various biocontainment levels. An example of a non-enveloped virus is Foot and Mouth Disease Virus (FMDV), a contagious pathogen of livestock. Due to its infectivity and environmental stability, outbreaks can lead to catastrophic economic losses. To conduct the study at a lower biocontainment level, we used Bovine Rhinitis B virus (BRBV), a genetically closely related surrogate for FMDV. First, we assessed the inactivation capacity of shampoos and leave-in conditioners directly against BRBV and an enveloped virus for comparison using liquid suspension assay. We show that only one shampoo inactivated BRBV; however, similar to disinfectant agents, all shampoos tested inactivated the enveloped virus. Co-wash and leave-in conditioner products showed neither antiviral activity against BRBV nor the enveloped virus. Second, we investigated the mechanical removal of BRBV on hairs using four different hair products and water, mimicking a personal shower. We used mannequin heads styled with various hairstyles, made of synthetic or human hair. A 3-min active shampoo massage followed by a 2-min water rinse was performed for all hairstyles and hair types. We found that water alone removed BRBV particles from most hairstyles and hair types. Exceptions were observed for one treatment using a synthetic voluminous curly/kinky hairstyle and two treatments involving mannequin head equipped with 100 synthetic braids. This study enhances our understanding of the critical role of personal protective measures in biocontainment facilities. It underscores the necessity of a minimum 2-min shower after exposure to non-enveloped animal viruses such as BRBV and highlights the need to develop specific shower procedures tailored to different hairstyles and hair types.IMPORTANCEShower-out procedures are a critical yet understudied component of biocontainment practices, particularly for preventing fomite transmission of highly stable, non-enveloped viruses. This study provides the first experimental, evidence-based evaluation of virus removal from hair using a surrogate for Foot and Mouth Disease Virus, addressing a significant gap in biosafety knowledge. By systematically assessing the roles of hair products, water rinsing, hairstyles, and hair types, we demonstrate the mechanical removal through rinsing, rather than chemical inactivation by shampoos, is the primary determinant of viral decontamination for most hairstyles. Importantly, our findings identify hair volume and density as key factors for viral persistence, especially in high-volume synthetic hairstyles. Additionally, the observed residual virus following co-wash treatment suggests that oil-rich, low surfactant hair products may impede mechanical virus removal and represent an overlooked risk factor in shower-out practices for high-containment personnel.