Warts are the most frequent viral infection we see in the podiatry clinic, yet in terms of research, we know little about how they are transmitted. Warts are caused by the Human Papilloma Virus, a large group containing many sub-types. In terms of warts, we know from previous research that the subtypes HPV1, HPV2, HPV4, HPV27 and HPV57 are the most frequent being responsible for around 86% percent of warts including the common and plantar (verrucae) varieties [1].
In a study published in the January 2022 edition of the Journal of the European Academy of Dermatology and Venereology [2], researchers have published further data from a study initially published in 2015. Back then, they undertook a randomised controlled trial looking at the effectiveness of monochloroacetic acid versus salicylic acid and cryotherapy [3] but in this latest paper they examined skin swabs taken from the patient with a plantar or common wart (from the wart surface), their forehead, the forehead of family members and swabs from their kitchen towel and bathroom mat. Following the collection of the swabs, samples were analysed using a PCR technique which is able to detect a wide range of HPV subtypes including the majority of those which cause skin infection.
In total, 62 families (466 swabs) were included in the analysis (62 patients with warts and 156 of their family members). The swabs of the patient’s warts showed the most prevalent subtypes as HPV27, HPV1, HPV57 and HPV2 respectively. The subtype HPV1 occurred most often in the younger patients (under the age of 10) than other subtypes which were more frequent in the teenage years. Plantar warts were generally of the HPV 1, HPV 27, HPV 57 and HPV 2 subtypes. Curiously, 46% of patients (with warts) and nearly 43% of their family members (without warts) carried HPV virus on their forehead.
When examining the data further, the spread of HPV types 1 and 2, differed from HPV 27 and HPV 57. When HPV 1 & 2 were detected as the patient's wart, there was a high prevalence of this type of HPV (70%) on the forehead of the patient, their family members and from swabs of kitchen towels (45%) and bathroom mats (60%). Subtypes HPV 27 & 57 were much less frequently detected in the surroundings (25%).
This is the first published study that has looked at the presence of the virus in household locations. So, what does this work tell us? Firstly, we can only assume that the infection pathway was from the patient’s wart to the forehead, kitchen towel and or bathmat. This occurred more readily with the HPV 1 and 2 subtypes in this study. As we know from this, and earlier work, the HPV 1 subtype is more common in children under 12 years old and usually only remains for about 6 months on average on the skin as a wart before natural resolution occurs. The HPV1 subtype is more common on the soles, whilst the HPV2 is more common on the hands of older children. There was a low number of family members infected as well with the HPV1 and 2 subtypes suggesting low transmissibility to family members.
So, should measures be taken with the towels and bathmats in the homes of our verrucae patients? Well, this was the first study to examine the transmission - further work is needed to corroborate these findings. However, on the face of it, looking at the high transmission of HPV1 & 2 via these materials one could say yes, but actual transmission and subsequent infection rates to other family members were generally low in this study, despite high carriage rates of HPV on the forehead. The HPV virus can survive for about a week or longer on hard surfaces [4, 5] but less so if the surface is dry or desiccated [6]. In addition, the HPV virus begins to be inactivated at around 56 degrees centigrade and is completely eliminated at 100 degrees centigrade so any cleaning of linen would require boil washing to ensure complete eradication of particles which may be impractical in a household setting as reuse by the patient with warts would quickly re-introduce infection. Ultimately, it would be good to see further work examine the transmission of HPV infections but as this study shows, family members may carry the infecting virus but do not often show clinical infection (namely warts).
References
1. Bruggink SC, de Koning MNC, Gussekloo J, Egberts PF, ter Schegget J, Feltkamp MCW, Bavinck JNB, Quint WGV, Assendelft WJJ, Eekhof JAH: Cutaneous wart-associated HPV types: Prevalence and relation with patient characteristics. J Clin Virol 2012, 55(3):250-255.
2. Ghorzang E, de Koning MNC, Bouwes Bavinck JN, Gussekloo J, Quint KD, Goeman JJ, Feltkamp MCW, Bruggink SC, Eekhof JAH: HPV type-specific distribution among family members and linen in households of cutaneous wart patients. J Eur Acad Dermatol Venereol 2022, 36(1):119-125.
3. Bruggink SC, Gussekloo J, Egberts PF, Bavinck JN, de Waal MW, Assendelft WJ, Eekhof JA: Monochloroacetic acid application is an effective alternative to cryotherapy for common and plantar warts in primary care: a randomized controlled trial. J Invest Dermatol 2015, 135(5):1261-1267.
4. Ding D-C, Chang Y-C, Liu H-w, Chu T-Y: Long-term persistence of human papillomavirus in environments. Gynecol Oncol 2011, 121 1:148-151.
5. Egawa N, Shiraz A, Crawford R, Saunders-Wood T, Yarwood J, Rogers M, Sharma A, Eichenbaum G, Doorbar J: Dynamics of papillomavirus in vivo disease formation & susceptibility to high-level disinfection-Implications for transmission in clinical settings. EBioMedicine 2021, 63:103177.
6. Roden RB, Lowy DR, Schiller JT: Papillomavirus is resistant to desiccation. J Infect Dis 1997, 176(4):1076-1079.