In markets where the first case of infection had already been recorded, the negative reaction of investors was greater than in markets where the first case had not yet been found. Implications / Recommendations: A small number of cases and high uncertainty about COVID-19 have a more substantial negative impact on investors than a high number of cases coupled with a better understanding of the pandemic. WHO announcements further contributed to the occurrence of stronger declines in countries in which people had already become infected by COVID-19. Contribution: The current study is the first of its kind, focusing not only on the first case of COVID-19, but also on other focal points of the evolving pandemic. The other aspects (month, WHO announcements) covered are also analysed from a different, broader view than in other studies.Article type: original article.