Are warts seasonal?
Now that is an interesting thought. The idea that warts might be seasonal? In dermatology, there are quite a few conditions which may show seasonality - that is a predictable rise and fall throughout certain times of the year. For example, psoriasis tends to be worse in the autumn and winter, allergies can arise during certain times of the year and dry skin is most often seen in the winter months. Published work has even suggested how things like cellulitis  and onychomadesis  may have annual variations. The seasonality can be due to various environmental changes associated the time of year – a rise or fall in temperature, changes in UV light levels or allergens in the atmosphere for example. For some viral infections it is well known that occurrence tends to be seasonal (such as slapped cheek disease arising in late winter and early spring, gloves and socks syndrome in spring and summer) but what about the Human Papilloma Virus and warts – is it possible?
This is a topic of discussion in a short paper due for publication in the American Academy of Dermatology . Proving such seasonal variation with the infection can be tricky but the authors took an interesting approach. Google collects massive amounts of data on search trends which is freely available for analysis. The dataset records the search term, location, time, and the magnitude of inquiries. Google has been collecting data regularly since 2004. By accessing this dataset, it is possible to look at trends in global search queries.
The authors undertook the research using the Google Search engine, they analysed search inquiries for three types of viral infection - “wart”, “genital wart” (GW) and “molluscum contagiosum” (MC). What they found was interesting. For warts and MC there was a definitive seasonal pattern evident, which showed a roughly biphasic pattern over the course of a year. The seasonality was compared by matching northern hemisphere countries with southern hemisphere countries and showed inverse curves which reinforced the notion of a seasonal pattern. However, there was no seasonality seen for GW’s which remained more or less constant regardless of the time of year.
This is an interesting result, but as the authors point out there are a few things to bear in mind. Firstly, seasonality was apparent for many of the countries analysed (including the UK, USA, Japan, Canada, Australia and Russia) but some countries lacked this trend (including Romania, Iran, Kazakhstan, Philippines, Kenya, South Africa, Ecuador, Colombia, Peru and Brazil). Secondly, that search trends on Google only represent a patient’s interest which may not necessarily reflect the time of year the disease is really occurring but perhaps just the person's specific interest in their skin condition at that time. For example, when more of a patient’s skin is exposed (in the summer months) are they more self-conscious of the infection and seeking internet advice? My own comment on this work is also around wart chronicity. As podiatrists, we are well aware that most warts on the feet will linger for a year or more. At that point, does seasonality become a blurred issue? Certainly for viral diseases with short durations (such as hand, foot and mouth) they come and go in a matter of weeks making it easier to spot a seasonal trend but warts with their notoriously longer duration and this will have an impact on the results.
1. Haydock, S.F., et al., Admissions to a U.K. teaching hospital with nonnecrotizing lower limb cellulitis show a marked seasonal variation. British Journal of Dermatology, 2007. 157(5): p. 1047-1048.
2. Pearson, H.J., R.T. Brodell, and C.R. Daniel Iii, Seasonal Onychomadesis of the Great Toes. Skin appendage disorders, 2018. 4(3): p. 177-179.
3. Phelan, P.S., Y.R. Semenov, and Z.P. Nahmias, Worldwide seasonal variation in search volume for cutaneous warts from 2004 to 2019. Journal of the American Academy of Dermatology, 2020: in press.