The webpage ”H5 Reference Laboratories” on the WHO Global Influenza Surveillance and Response System (GISRS) site describes a network of specialized laboratories designated by the World Health Organization to support global influenza monitoring — particularly for H5 subtype avian influenza viruses. It explains that these reference laboratories perform high-level testing, characterization, and sharing of influenza virus samples, including genetic sequencing and antigenic analysis. Their role is to help detect and assess influenza virus strains of public health concern (especially H5 strains with pandemic potential), support vaccine strain selection, and provide technical guidance and capacity building to national influenza centers and other laboratories. The page highlights the importance of this global laboratory network in strengthening early warning, risk assessment, and preparedness for influenza outbreaks and pandemics.