Seasonal influenza viruses are circulating widely in the Southern Hemisphere, but influenza activity is currently low in the United States, according to research published in the Oct. 11 issue of the U.S. Centers for Disease Control and Prevention Morbidity and Mortality Weekly Report.

Scott Epperson, D.V.M., from the CDC in Atlanta, and colleagues describe influenza activity from May 19 to Sept. 28, 2019, in the United States and worldwide.

The researchers note that low levels of influenza activity were reported in the United States during the study period, with cocirculation of influenza A and influenza B viruses. Seasonal influenza viruses circulated widely in the Southern Hemisphere, with influenza A(H3) predominating in many regions; in some countries, influenza A(H1N1)pdm09 and influenza B viruses were predominant. The World Health Organization recommended components for the 2020 Southern Hemisphere influenza vaccine in late September and included an update to the A(H3N2) and B/Victoria-lineage components. For preventing influenza illness and its complications, annual influenza vaccination is recommended, and vaccination before increases in influenza activity is optimal. Vaccination should be recommended for all persons aged ≥6 months without contraindications to vaccination.

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