Internet search data have been shown to enable the monitoring of Middle East respiratory syndrome 3 days before laboratory confirmations [9]. However, our results showed a much longer lag time for reported new laboratory-confirmed and suspected COVID-19 cases compared with digital surveillance data. There are several explanations. Firstly, COVID-19 is a novel disease just recently recognised. The first version of a guideline for diagnosis and management of COVID-19 was announced on 16 January 2020. It took time for the medical professionals to learn about the virus and the disease in order to make correct diagnosis. Secondly, the diagnosis of COVID-19 requires two independent confirmatory laboratory tests, which should be taken at least 1 day apart. Our results showed that the lag correlation is shorter for the suspected than for laboratory-confirmed cases. Thirdly, the supply of laboratory testing kits may have been insufficient in the early stages of the coronavirus outbreak, which would have limited the number of patients that can be confirmed. Finally, the Internet searches and social media mentions are not only initiated by the patients and their family members, but also globally by the general public who are concerned about this rapidly spreading disease.