  Our society is built on a complex web of interdependencies whose effects
become manifest during extraordinary events such as the COVID-19 pandemic, with
shocks in one system propagating to the others to an exceptional extent. We
analyzed more than 100 millions Twitter messages posted worldwide in 64
languages during the epidemic emergency due to SARS-CoV-2 and classified the
reliability of news diffused. We found that waves of unreliable and low-quality
information anticipate the epidemic ones, exposing entire countries to
irrational social behavior and serious threats for public health. When the
epidemics hit the same area, reliable information is quickly inoculated, like
antibodies, and the system shifts focus towards certified informational
sources. Contrary to mainstream beliefs, we show that human response to
falsehood exhibits early-warning signals that might be mitigated with adequate
communication strategies.
