Update: Influenza Activity in the United States During the 2018-19 Season and Composition of the 2019-20 Influenza Vaccine

• Published in: MMWR. Morbidity and mortality weekly report 2019-06, Vol.68 (24), p.544-551
• Main Authors: Xu, Xiyan, Blanton, Lenee, Elal, Anwar Isa Abd, Alabi, Noreen, Barnes, John, Biggerstaff, Matthew, Brammer, Lynnette, Budd, Alicia P, Burns, Erin, Cummings, Charisse N, Garg, Shikha, Kondor, Rebecca, Gubareva, Larisa, Kniss, Krista, Nyanseor, Sankan, O'Halloran, Alissa, Rolfes, Melissa, Sessions, Wendy, Dugan, Vivien G, Fry, Alicia M, Wentworth, David E, Stevens, James, Jernigan, Daniel
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Aged; Amino acids; Antiviral Agents - pharmacology; Child; Child Mortality; Child, Preschool; Cost of Illness; Drug Resistance, Viral; Full Report; Hospitalization - statistics & numerical data; Humans; Infant; Infant Mortality; Infant, Newborn; Influenza; Influenza A Virus, H1N1 Subtype - drug effects; Influenza A Virus, H1N1 Subtype - genetics; Influenza A Virus, H1N1 Subtype - isolation & purification; Influenza A Virus, H3N2 Subtype - drug effects; Influenza A Virus, H3N2 Subtype - genetics; Influenza A Virus, H3N2 Subtype - isolation & purification; Influenza B virus - drug effects; Influenza B virus - genetics; Influenza B virus - isolation & purification; Influenza vaccines; Influenza Vaccines - administration & dosage; Influenza Vaccines - chemistry; Influenza, Human - epidemiology; Influenza, Human - mortality; Influenza, Human - prevention & control; Influenza, Human - virology; Middle Aged; Outpatients - statistics & numerical data; Peramivir; Pneumonia - mortality; Population Surveillance; Seasons; Severity of Illness Index; United States - epidemiology; Vaccines; Young Adult
• ISSN: 0149-2195; 1545-861X; 1545-861X
• DOI: 10.15585/mmwr.mm6824a3

Influenza activity* in the United States during the 2018-19 season (September 30, 2018-May 18, 2019) was of moderate severity (1). Nationally, influenza-like illness (ILI) activity began increasing in November, peaked during mid-February, and returned to below baseline in mid-April; the season lasted 21 weeks, making it the longest season in 10 years. Illness attributed to influenza A viruses predominated, with very little influenza B activity. Two waves of influenza A were notable during this extended season: influenza A(H1N1)pdm09 viruses from October 2018 to mid-February 2019 and influenza A(H3N2) viruses from February through May 2019. Compared with the 2017-18 influenza season, rates of hospitalization this season were lower for adults, but were similar for children. Although influenza activity is currently below surveillance baselines, testing for seasonal influenza viruses and monitoring for novel influenza A virus infections should continue year-round. Receiving a seasonal influenza vaccine each year remains the best way to protect against seasonal influenza and its potentially severe consequences.