The Centers for Disease Control and Prevention lists current and past flu season information on its website, including the name of the currently circulating flu strain. The CDC also offers a weekly U.S. influenza survey on its website. Flu.gov also provides information on the current flu situation in the United States. The website gives important news updates on the virus, as well as more detailed information on specific strains, such as avian influenza A and swine flu (H1N1).
The CDC weekly survey consists of two reports: FluView and FluView Interaction. The reports detail viral surveillance, pneumonia and influenza mortality, influenza-associated pediatric deaths, outpatient illness surveillance, and the geographic spread of the virus. Using these reports, patients can see which influenza virus was most prominent week by week. However, flu viruses constantly change, making it common for new viruses to emerge each year, states the CDC.
Nevertheless, the yearly flu vaccine is developed after researching which flu strains are most likely to be dominant in the upcoming season. For example, the CDC states that the 2015-2016 flu vaccine protected against influenza A viruses H1N1 and H3N2. However, different strains strike at different times in the season, explains the CDC. For example, in the 2013-2014 flu season, the 2009 H1N1 strain dominated the first part of the season while influenza B strains dominated the latter part of the season.