The skin as a target for SARS-CoV-2 infection: exploiting the web for suitable data.

In this issue of the BJD, Visconti et al. present the results of a mobile app survey of symptoms related with SARS‐CoV‐2 infection, combined with an independent web‐based data collection of skin manifestations and clinical pictures in patients presumably infected by the virus, for expert review. The study documents that self‐reported transient skin rashes, classifiable a posteriori by experts as papular rashes, urticaria or acral lesions, are more frequent in people testing positive on a swab for SARS‐CoV‐2 than in people testing negative, and in untested users with a history of at least one of the three main symptoms of COVID‐19 (i.e. fever, persistent cough and/or anosmia) than in people lacking any of these symptoms. Notably, in about 38% of people testing positive for SARS‐CoV‐2 (either by swab or by antibodies) and reporting skin manifestations, cutaneous symptoms either appeared before any other symptoms or were the only clinical manifestation. Rather surprisingly, the association of a positive SARS‐CoV‐2 test was stronger for any skin rash than for fever, an established symptom of COVID‐19, the odds ratios for the associations being 1·67 and 1·48, respectively.

Not only does this study add to the increasing body of evidence pointing to the skin as a target for SARS‐CoV‐2 infection, but it also suggests that cutaneous manifestations may represent an early sign and a clue for the diagnosis. In addition, this study emphasizes the vital role that web‐based applications may play in overcoming the difficulties posed by distancing during the pandemic. Finally, it reinforces the importance of direct involvement of patients in improving health care.

As of October 2020, almost 4·66 billion people (59% of the global population) are active internet users, mainly through mobile phones. It is not surprising that, in spite of recognized limitations and concerns, the internet is increasingly relied on in clinical and epidemiological research. Terms such as ‘infodemiology’, ‘internet epidemiology’ and ‘e‐epidemiology’ have been used to refer to the exploitation of internet resources in epidemiological and public health research. , ,

Self‐selection for participation and reliability of self‐reported data are the main reasons for concerns with web‐based data. Less‐educated and older people are less prone to use the internet and are under‐represented in web‐based surveys. The pandemic has acted as a catalyst for implementing web‐based resources and services, but more research is needed to understand the advantages and limitations of internet tools for research purposes.

Identifying SARS‐CoV‐2‐related skin rashes is important for early detection of infected patients, but relevant issues are still open. In particular, it is important to understand how skin manifestations cluster with other COVID‐19‐related symptoms, to enable the development of a comprehensive predictive score system for SARS‐CoV‐2 infection. It is also unclear whether skin manifestations reflect a peculiar pathomechanism and if they are influenced by pre‐existing cutaneous diseases. Their relation with long‐term sequelae and their response to vaccines are also unexplored. It is conceivable that some of these questions will be addressed in future studies by relying on web‐based data collection linked with routinely collected healthcare data, census information and, possibly, ad hoc performed laboratory examinations.