  An infodemic is an emerging phenomenon caused by an overabundance of
information online. This proliferation of information makes it difficult for
the public to distinguish trustworthy news and credible information from
untrustworthy sites and non-credible sources. The perils of an infodemic
debuted with the outbreak of the COVID-19 pandemic and bots (i.e., automated
accounts controlled by a set of algorithms) that are suspected of spreading the
infodemic. Although previous research has revealed that bots played a central
role in spreading misinformation during major political events, how bots
behaved during the infodemic is unclear. In this paper, we examined the roles
of bots in the case of the COVID-19 infodemic and the diffusion of non-credible
information such as "5G" and "Bill Gates" conspiracy theories and content
related to "Trump" and "WHO" by analyzing retweet networks and retweeted items.
We show the segregated topology of their retweet networks, which indicates that
right-wing self-media accounts and conspiracy theorists may lead to this
opinion cleavage, while malicious bots might favor amplification of the
diffusion of non-credible information. Although the basic influence of
information diffusion could be larger in human users than bots, the effects of
bots are non-negligible under an infodemic situation.
