Introduction

People with multiple sclerosis (MS) frequently use search engines, such as Google, to look for terms related to their disease, and its possible causes and symptoms.1 ,2 The large number of searches conducted through Google creates trend data, and can be analysed with Google Trends, a publicly available tool that compares the volume of Internet search queries in different areas and periods.3 Therefore, Google Trends can provide indirect estimates of the burden of diseases and symptoms, and, accordingly, has been used for surveillance studies.3 For instance, Google Trends can precede traditional control systems in detecting seasonal or annual outbreaks of infectious (ie, influenza, scarlet fever, HIV) and non-infectious diseases (ie, cancer, epilepsy) presenting specific patterns in different parts of the world.3 Nevertheless, Google Trends for MS have positively been associated with disease prevalence in an Italian study.2

Different clinical and epidemiological studies have been conducted on seasonality of MS, and focused on relapses, fatigue and MRI. Overall, disease activity has been associated with specific seasonal patterns in both, Northern and Southern hemispheres, possibly in relation to sun exposure.4 ,5 Therefore, the present 10-year retrospective web-based research investigated the seasonality of Google Trends search volumes for ‘multiple sclerosis’ and for MS-related search terms, in the Northern and Southern hemispheres.