Outbreak of Highly Pathogenic Avian Influenza A(H5N1) Viruses in U.S. Dairy Cattle and Detection of Two Human Cases — United States, 2024
Authors: Shikha Garg, Carrie Reed, C. Todd Davis, Timothy M. Uyeki, Casey Barton Behravesh, Krista Kniss, Alicia Budd, Matthew Biggerstaff, Jennifer Adjemian, John R. Barnes, Marie K. Kirby, Colin Basler, Christine M. Szablewski, Malia Richmond-Crum, Erin Burns, Brandi Limbago, Demetre C. Daskalakis, Kimberly Armstrong, David Boucher, Tom T. Shimabukuro, Michael A. Jhung, Sonja J. Olsen, Vivien Dugan
Journal: MMWR Morbidity and Mortality Weekly Report (2024)

Comprehensive and timely information on influenza virus characteristics is critical for determining when the flu season starts and which viruses are circulating, for identifying and preparing viruses for use in influenza vaccines, and for detecting novel influenza viruses with potential for pandemic spread.In 2013, the first edition of the "Right Size Roadmap" was released.The document was the result of an initiative begun in 2010, led in partnership by the Centers for Disease Control and Prevention (CDC) and the Association of Public Health Laboratories (APHL) which engaged various stakeholders, including: epidemiologists, laboratorians, and influenza coordinators at local and state public health departments and at CDC; members and staff from the Council of State and Territorial Epidemiologists (CSTE); clinical and commercial laboratory associations; academic statisticians; and consultants in efficiency improvement.The goal of the effort was to support improved use of new tools for accurate and rapid molecular diagnosis of influenza, new opportunities for electronic communication of laboratory results, and to maintain or enhance virologic surveillance in the United States to detect first cases of emerging novel influenza A virus infection, such as infections with variant A(H3N2), or avian A(H5Nx) or A(H7N9) viruses.The resulting document provided a set of functional requirements to design and build an optimal virologic surveillance system, improve existing systems approaches, focus resources and efficiencies, inform policymakers, and justify state and local funding requests.It used statistical tools to determine the desired or acceptable level of surveillance and recommended efficiency approaches.Today we have a standardized sampling strategy across public health and clinical laboratories that is nationally representative, ensures efficiency and data confidence, and includes characterizing both the antigenic and genomic properties of circulating influenza viruses.The landscape of influenza virologic surveillance has changed significantly since the first edition with national surveillance of influenza having transitioned to rely on public health laboratories submitting a set number of influenza positive samples weekly to one of the National Influenza Reference Centers (NIRCs), established in 2009, where additional characterization including virus isolation and whole genomic sequencing are done.Resultant isolates and data are then compiled by the CDC for further characterization and analysis.In addition to identifying the optimum "sampling" strategy, major improvements in sharing these data have taken place.In March 2009, five laboratories were routinely sharing specimen level data electronically with CDC.Today, all public health laboratories at the state level and some local public health and clinical laboratories send specimen level data electronically to CDC's Influenza Division.This increase has improved the timeliness and completeness of reporting for both seasonal influenza surveillance activities and the identification of novel influenza A viruses.Influenza viruses are constantly changing, and efforts to monitor and characterize the virus similarly need to be flexible and adaptive to changes in healthcare, laboratory technology, and financial and staff resources.Equally, this second release will also change, and as such, continued input and feedback are invited to improve these recommendations for achieving a right size for influenza virologic surveillance.Future iterations will explore the possibility of utilizing the Right Size approach for non-influenza virus responses. Vivien DuganDirector, Influenza Division Centers for Disease Control and Prevention * Any influenza positive specimen that cannot be definitively typed and subtyped as a circulating seasonal influenza A virus, influenza positive specimens producing nonstandard or inconclusive results as defined in the CDC Flu rRT-PCR Dx Panel Instructions for Use package insert.