Dear Editor, Astroviruses (AstVs) (family Astroviridae) are positive-sense, single-stranded RNA viruses that infect a large diversity of mammalian and avian species. 1 In humans, eight serotypes have been described worldwide, accounting for 2%–9% of all acute non-bacterial gastro-enteritis cases in children. 2 AstVs have been detected from over 80 non-human host species, including a large diversity of bat species in Asia, Europe and Africa, 3 and recent phylogenetic analyses suggest that the long-term evolution of AstVs is determined by frequent cross-species transmission events. 4,5 During the past decade, numerous AstVs with potential zoonotic transmission have been described, highlighting the need for improved knowledge on their biology to prevent future health threats. 2 Bats are recognized as a major reservoir of infectious agents. Madagascar shelters over 46 bat species, of which nearly 80% are endemic, occupying different types of day roosts, including natural and synanthropic sites. Recent investigations have shown that the compositions of Malagasy bat species assemblages are correlated with factors associated with the diversity and transmission of infectious agents, such as paramyxoviruses and Leptospira. 6,7 The detection of new Betacoronaviruses in endemic Malagasy fruit bats also underlined the urgent need to better understand bat-associated infectious agents, and thus assess the potential for spillover to human populations in this major biodiversity hotspot. 8