# An Efficient UV-C Disinfection Approach and Biological Assessment Strategy for Microphones
## 4 Discussion  
Here, we present a facile disinfection device that can be used in events where microphones are predominantly used, which includes the entertainment industry but also conferences and other social events, to prevent the transmission of infectious agents.  
Because the M13 bacteriophage does not represent a threat to humans or animals, it was used here as a facile model to determine the efficacy of UV-C irradiation in the elimination of viral contaminations on microphones. Importantly, our verification experiments with PR8 H1N1 influenza virus showed that this virus was successfully eliminated by UV-C treatment with an efficacy that was indistinguishable from the efficacy at which the M13 bacteriophage was eradicated. However, it has to be noted that, for reasons of biosafety, these verification experiments were performed in solution, whereas the disinfection experiments with the foams and whole microphones involved dry surfaces contaminated with the M13 bacteriophage. Therefore, there might still be a difference in terms of the susceptibility of different viruses to UV-C treatment when present on dry surfaces.  
Based on the theoretical considerations and the known susceptibility to UV-C (influenza dose of 105 J/m\({}^{2}\) according to DIN 5031-10: 2018-03 [33] but lower values have been measured [21]), a 1-min irradiation at 373 uW/cm\({}^{2}\)--the lowest irradiance value measured in the device--would be sufficient to achieve 99.9% of viral inactivation (according to [33]). Our experiments demonstrated a 99.3% reduction in the viral load upon 10-min UV-C disinfection of whole microphones. We consider this result impressive regarding the complex construction of a microphone, which makes it very difficult to irradiate all deposited viral particles with equal efficiency.  
Although the present UV-C disinfection device was tested for microphones and the respective foams, the implications of this technology are much broader. In particular, disinfection strategies based on UV-C are of great interest in the medical field. The main challenge here is to apply a standardized methodology, which is difficult to achieve as the conditions can vary greatly. For instance, surfaces may be wet or dry, and microbial contaminants may be surface-bound or suspended, or strongly or weakly adherent. These factors could potentially cause differences in the overall efficacy of UV-C irradiation. Although, conditions may vary and responses can differ, here we show that when the controls are chosen properly, it is possible to approximate the UV-C treatment efficacy. Hence, not only  
Figure 4: Spray deposition of bacteriophage M13 on complete microphones, which were subsequently subjected to disinfection by using UV-C. Extraction of M13 was performed by full submersion of the microphones in water combined with shaking. The amounts of M13 extracted from infected and disinfected microphones were compared, and the total reduction of active virus was determined.  
the here-described device for disinfection can be regarded as a valuable tool, but also our established methodology for contaminating surfaces and re-extracting viral particles may contribute to standardizing UV-C-induced disinfection strategies.