Fig. 1: How infodemics work.

Human (circles) and non-human (squares) accounts participate in the spread of news across a social network. Some users (A and B) create unreliable content, such as false or untrustworthy news or unsupported claims, while others (C) create content informed by reliable sources. When the topic attracts worldwide attention as in the case of COVID-19, the volume of information circulating makes it difficult to orientate oneself and to identify reliable sources. Indeed, some users (D) might be exposed to unreliable information only, while others (E and F) might receive contradictory information and become uncertain as to what information to trust. This is exacerbated when multiple spreading processes co-occur, and some users might be exposed multiple times to the same content or to different contents generated by distinct accounts.