Showering out of a high-containment laboratory is an established personal decontamination practice, but new research suggests that its effectiveness can depend on factors that standard protocols may not fully account for, including hair type, style, volume, and the products used during washing.
Researchers at the Galveston National Laboratory at the University of Texas Medical Branch evaluated how effectively different showering practices and hair products inactivated or removed viruses from hair. The study, published in Microbiology Spectrum, addresses a longstanding evidence gap in biocontainment practices. According to the American Society for Microbiology (ASM), the last relevant study examining the issue was published in 1967.
For laboratory leaders responsible for high-containment operations, the findings offer new information for reviewing personal decontamination procedures alongside other elements of a comprehensive biosafety program.
Researchers simulate shower-out procedures
Because the researchers wanted to conduct the experiments at a lower biosafety level, they used bovine rhinitis B virus (BRBV), a non-enveloped BSL-2 surrogate genetically related to foot-and-mouth disease virus. They also used Hazara virus as an enveloped-virus surrogate for comparison.
First, the team assessed four shampoos, one co-wash, and three leave-in conditioners using liquid suspension assays. All four shampoos inactivated the enveloped Hazara virus, while only one shampoo showed antiviral activity against the non-enveloped BRBV. The co-wash and leave-in conditioners showed little or no antiviral activity.
Researchers then evaluated physical virus removal using mannequin heads fitted with synthetic or human hair. Synthetic hair included straight, curly/kinky, loose locs, and sets of 45 and 100 braids. Human hair included straight/wavy, curly/kinky, and locs. The mannequin heads were exposed to BRBV and allowed to dry before researchers simulated showering. Hair was massaged with one of three shampoos or a co-wash for three minutes and then generally rinsed for two minutes. Water-only rinses served as a mechanical-removal control.
After washing, researchers collected hair from the front, center, and back of each mannequin head and tested the samples for residual infectious virus using cell culture.
Rinsing drives virus removal for most hair tested
The experiments indicated that mechanical removal through rinsing, rather than antiviral activity from shampoo, was the primary factor in removing BRBV from most hair types and styles tested. A water-only rinse removed detectable virus from most of the mannequin heads.
There were exceptions. Residual virus was detected in one treatment involving dense synthetic curly/kinky hair and in treatments involving 100 synthetic braids. The researchers found no residual infectious BRBV in the comparable 45-braid model under the same washing conditions, suggesting that hair volume and density can affect how thoroughly water and shampoo reach all areas.
“Our findings suggest that current shower-out procedures can be optimized,” lead author Anastasia Accoti, PhD, said in the ASM release. She added that standard “one-size-fits-all” shower protocols may not be optimal.
Findings could inform biosafety protocol review
For managers of high-containment facilities, the study provides an example of why biosafety procedures should account for variation among personnel rather than assuming one procedure performs identically under all conditions. Factors such as minimum rinse time, washing technique, hair volume and density, and products permitted or supplied by the facility could be considered when reviewing shower-out SOPs. The findings also reinforce the value of pairing written procedures with ongoing biosafety training and staff engagement.
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The researchers caution that the experiments do not represent every real-world scenario. The study used surrogate viruses rather than foot-and-mouth disease virus, mannequin heads rather than personnel, and a limited selection of human and synthetic hair. The authors also could not establish an exposure dose that directly represents contamination from an animal infected with foot-and-mouth disease virus. They acknowledge that real-world variation in hair and extensions is considerably broader than what they tested.
Those limitations make the findings a starting point for evidence-based protocol development rather than a universal shower-out standard. For laboratory leaders, they also highlight the importance of periodically reassessing biological hazard handling and safety practices as new evidence becomes available.
This article was created with the assistance of Generative AI and has undergone editorial review before publishing.
