Considering the emergence and dissemination of Influenza A/H5 avian outbreaks to multiple countries in the Americas and the risk of zoonotic infection, it is important to be prepared to respond, and the laboratory tests that are used to detect influenza A/H5 in human samples and the testing algorithm recommendations should be established. Information on suspected case definition; specimen collection; reagents; testing algorithm and shipment; effective usage of global laboratory networking; and reporting of cases and test results can be found in this interim guidance.