Scabies, which is classified as a neglected tropical disease by the World Health Organization, is an ectoparasitic dermatosis caused by the Sarcoptes scabiei var. hominis mite, which lives and reproduces in humans.1 Although in the past, scabies was typically associated with situations of poverty, poor hygiene, and overcrowding due to wars, forced displacement, and economic crises, it is currently endemic in many developing countries, and epidemiologically, it can now be considered a broadly global disease.2

It is difficult to estimate the global prevalence and impact of scabies, in part because of the associated stigma and because it is not a notifiable disease in most countries.3 Nonetheless, the number of scabies cases diagnosed in Spain has been on the rise since 2014, with some studies suggesting a recent explosion4,5 and similar reports from other European countries.6–8 Because, however, there are no epidemiological surveillance programs for scabies in Spain, the true magnitude of the epidemic in our country is unknown.

One way of tracking changes to the incidence of diseases not covered by traditional epidemiologic surveillance systems in the public health field is to analyze drug sales data. Another potentially useful method for indirectly estimating certain epidemiologic characteristics of many health conditions, including skin infestations, is to analyze public interest via internet search trends in a given country or region over time.9–11 Google Trends is a free tool that can be used to analyze changes in the popularity of Google search terms applied to specific time periods and places.12 The tool uses a measure called relative search volume (RSV), which has a scale of 0 to 100, where 100 indicates the highest percentage of searches for a term in a given place and time. An RSV of 0 does not necessarily mean that no searches were conducted; it simply indicates low interest relative to terms with a peak RSV (RSVmax).

Google Trends offers several advantages, including a free, simple, and fast tool for analyzing real-time changes in a large database and comparing searches across topics, periods, and geographic areas. It also has its limitations. Notably, people older than 65 years use the internet less, the data provided are relative, and it is not possible to stratify by age, sex, or other variables of interest.

The aim of this study was to complement existing evidence on the increasing number of scabies cases in our country by analyzing changes in ectoparasiticide prescriptions and internet searches for scabies infestations measured by Google Trends. We also examined correlations between these 2 variables.

We conducted a targeted search of ectoparasiticide sales (code P03A) on the Spanish Ministry of Health website13 and collected annual data for the years 2009 to 2021 and monthly data from January 2020 to February 2022.

We also examined Google search volumes for terms relating to scabies in Spain for the period January 2004 to June 2022. The terms used were sarna and escabiosis (Spanish terms for scabies), and escabiosi (the Catalan term). Terms such as itch, pruritus, and treatment resistance were excluded as they were considered nonspecific. The Google Trends search was conducted on June 27, 2022.

Statistical analyses were conducted in the software program StatPlus. For the descriptive analysis, mean and standard error of the mean (SEM) were used as measures of central tendency and dispersion, respectively. Correlations between variables were studied using linear correlation analysis.

We observed an explosion in pharmacy sales of ectoparasiticides in Spain between 2020 and 2021. The number of packages sold does not reflect the number of patients treated, making it impossible to distinguish between increases due to a rise in patients or a rise in prescriptions per patient (e.g., prescriptions for the whole family or repeat treatments). We assume that the changes observed are more indicative of an increase in scabies than in other ectoparasitic infections, as the latter are much less common in Spain. This “large-scale national outbreak” has been attributed to COVID-19 lockdown measures and possible resistance to conventional treatments.14,15

Google searches for terms related to scabies have also shown a rising trend since 2004, with a notable increase observed since the end of 2012. Internet search volumes are a good indicator of public interest in a given topic, but they do not necessarily correlate with epidemiological phenomena. Many factors can drive public interest in a topic, including media coverage, commercial or advertising interests, novelty, and topics with a temporary or periodic nature.

Our data for Spain show that monthly ectoparasiticide sales were strongly and positively correlated with Google searches for scabies during the same period.

Sales and internet search volumes were also higher in winter than summer months, although the difference did not reach statistical significance. Infestations would be expected to be more prevalent in winter, as mites are able to survive for longer outside the host in humid, cold conditions.1,16

We observed a sharp drop in RSV following the peak in February 2022, but were unable to compare this to ectoparasiticide sales for the same period as the data had not been published at the time of writing. Perhaps the drop in search volume will ultimately be reflected in a drop in scabies cases, and with it, a drop in ectoparasiticide sales.

Public interest in scabies and ectoparasiticide sales in Spain have increased in recent years and show a strong, positive correlation. Despite its limitations, Google Trends could be considered as a complementary tool for monitoring real-time trends in scabies infestations in Spain.

The authors declare that they have no conflicts of interest.