Infectious lower respiratory diseases and diarrheal diseases are the leading causes of death globally . And the ongoing COVID-19 pandemic, which has contributed to 4.1 million deaths in 2019, once again is reminding the necessity of proactively identifying early signs of infectious disease outbreaks before things are getting worse. Conventional microbial diagnostics techniques would identify pathogens under specific culture conditions by serological detection of pathogen-associated antibodies or microbial genetic investigation using PCR, but these methods have been seen obvious shortcomings in pathogen coverage. It's highly required to find advanced scientific tools that are more sensitive even with a low microbial load or when targeted microorganisms are not suitable for in vitro culture, for which metagenomic approaches that can profile all DNA or RNA of a patient sample are increasingly catching the eyes of researchers. How metagenomics can be used in infect...