The 2018-2019 influenza season in the United States was of moderate severity and lasted 21 weeks, making it the longest in 10 years, researchers from the CDC’s Influenza Division reported in MMWR.
Preliminary estimates placed the total number of influenza-associated deaths in the U.S. between 36,400 and 61,200, the researchers wrote. There were 116 laboratory-confirmed pediatric deaths from influenza.
Between Sept. 30, 2018, and May 18, 2019, public health laboratories tested 80,993 specimens for influenza virus. Among 38,995 seasonal influenza A viruses subtyped, 22,084 (56.6%) were influenza A(H1N1)pdm09, and 16,991 (43.6%) were influenza A(H3N2).
H1N1 accounted for most circulating viruses in the U.S. from October to mid-February, followed by a wave of H3N2 from late February through mid-May. The two waves of influenza A — and low prevalence of influenza B, which accounted for just 4% of viruses reported by public health laboratories — made 2018-2019 different from recent seasons, the researchers wrote.
The 2018-2019 influenza season was of moderate severity and featured two waves of influenza A activity
Source: CDC/Dan Higgins
Hospitalization rates this season were lower for adults but similar for children compared with the severe 2017-2018 season, in which an estimated 900,000 people were hospitalized and 80,000 died. This season, the cumulative influenza-associated hospitalization rate per 100,000 population was 72 among children aged 0 to 4 years, 20.4 among children and adolescents aged 5 to 17 years, 25.8 among adults aged 18 to 49 years, 80.7 among adults aged 50 to 64 years and 221.7 among adults aged 65 years or older, the researchers reported.
They estimated that influenza caused up to 42.9 million symptomatic illnesses and led to as many as 20.1 million medical visits and 647,000 hospitalizations this season.
“This season underscores the unpredictability and ever-present potential for severe illness related to flu and the fact that public health partners need to keep working to expand the use of our existing tools to fight flu but also to create better vaccines and better treatment options,” study author Xiyan Xu, MD, told Infectious Disease News. – by Joe Gramigna
Disclosures: The authors report no relevant financial disclosures.