In this article, we analysed the 100 most engaging contents about COVID-19 on social networks in Brazil, in March 2020, when the disease officially arrived in the country. Within the infodemic context, we analysed the accuracy of the information and the reliability of the websites that guided the debate. Our results show that misinformation/disinformation accounted for 13.5% of the sample and that their average engagement was greater than the one for the information that could be verified in other sources and in accordance with scientific evidence. We also found that professional websites, especially journalistic ones, predominate among sources. The results point to the need to combine science communication strategies with network communication dynamics.