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. 2022 Jul 29;12:13083. doi: 10.1038/s41598-022-17396-5

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© The Author(s) 2022

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

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Sampling effort by month for both the USDA national surveillance program and the NIAID Influenza Research Database (IRD) datasets and map of the waterfowl flyways. USDA provides greater coverage across the continental United States as sampling was stratified by flyway and watershed. The majority of IRD sampling events are located either in the Mississippi (M) and Central (C) Migratory Flyways, California and Alaska in the Pacific (P) Migratory Flyway, and Maine and Delaware in the Atlantic (A) Flyway. However, IRD adds greatly to the total sample coverage during the spring lull in sampling effort. Maps were produced in ggplot2⁶⁸.