Look to the NIH website for more information.
Emerging viruses have been a concern for some time.
From the abstract of a paper that was published in September 2019 called, "Emergence and Reemergence of Viral Zoonotic Diseases: Concepts and Factors of Emerging and Reemerging Globalization of Health Threats."
The unpredictable emergence of new zoonotic diseases with viral etiology is currently a hot issue in the scientific and political circles. Viral emergence and reemergence, as a sanitary event, are only the visible part of the iceberg, while the hidden one corresponds to a multitude of complex and interrelated factors, including societal and environmental factors favoring the advent of the state of viral emergence and reemergence.
According to the World Health Organization, 60% of the agents recognized as human pathogens come from the animal kingdom, and 75% of the pathogens responsible for emerging and reemerging animal diseases present a potential transgression of interface between interspecies establishing favorable conditions for genetic exchange leading to the emergence of new highly pathogenic variants and strains of which the animal is often the host reservoir.
Further down:
Bat-borne zoonotic diseases add a supplementary challenge to the global health community and their role has been demonstrated in the emergence and reemergence of many serious and highly publicized viral infectious diseases [Ebola and Marburg virus (reemergence in 2014), Hendra virus (emergence since 1994), Nipah virus (emergence since 1997)].