According to US researchers, the United States may serve as a breeding ground for certain flu strains, aiding in their migration to warmer climates. It was previously believed that flu strains mainly originated from China and Southeast Asia, but a study involving the University of Michigan, the Howard Hughes Medical Institute, and Florida State University discovered that some flu strains in North America do not disappear at the end of flu season. Instead, some of these strains travel to South America and even further. This may have been the case with the H1N1 swine flu pandemic. Trevor Bedford of the University of Michigan, along with his colleagues, conducted a study that found China and Southeast Asia are major players in the influenza A migration network, but temperate regions like the USA also play a significant role. They analyzed genetic sequences from seasonal flu viruses collected worldwide between 1998 and 2009, creating a family tree to show relationships among the viruses. This new understanding of flu could lead public health officials to reconsider their strategies for combating the virus, as the aggressive use of antiviral drugs like Tamiflu could potentially promote drug resistance if certain flu strains persist in the United States. Bedford stated that South America primarily gets its flu strains from North America, suggesting that a vaccine tailored to North American strains may be more effective. The research findings can help improve tracking of flu strains globally, providing insight into the origins of influenza outbreaks. Bedford emphasized the need for more comprehensive surveillance of flu viruses to better understand their global spread. The initial instances of H1N1 swine flu were identified in the United States. It is unclear where the swine flu originated, but genetic research indicates that it likely came from pigs and had been present for a long time before it was discovered.