Five influenza-associated pediatric deaths occurring in weeks 52 (the week ending December 28, 2019) and 1 (the week ending January 4, 2020) were reported to CDC during week 1. Three were associated with influenza B viruses that did not have a lineage determined, and two were associated with influenza A(H1N1)pdm09 viruses. A total of 32 influenza-associated pediatric deaths occurring during the 2019-2020 season have been reported to CDC. Twenty-one deaths were associated with influenza B viruses. Five of these had the lineage determined and all were B/Victoria viruses. 11 deaths were associated with influenza A viruses. Six of these had subtyping performed and all were A(H1N1)pdm09 viruses.
Levels of outpatient ILI remain elevated; however hospitalization rates and percent of deaths due to pneumonia and influenza remain low. This is likely due to the predominance of influenza B/Victoria and influenza A(H1N1)pdm09 viruses which are more likely to affect children and younger adults than the elderly. Because the majority of hospitalizations and deaths occur among people age 65 and older, with fewer illnesses among that group, we expect, on a population level, to see less impact in flu-related hospitalizations and deaths.
The decline in outpatient ILI and laboratory data this week may in part be influenced by changes in healthcare seeking behavior and influenza virus transmission that can occur during the holidays. It is too early to know whether the season has peaked or if flu activity will increase into January.
CDC estimates that so far this season there have been at least 9.7 million flu illnesses, 87,000 hospitalizations and 4,800 deaths from flu.
It’s not too late to get vaccinated. Flu vaccination is always the best way to prevent flu and its potentially serious complications.
Antiviral medications are an important adjunct to flu vaccine in the control of influenza. Almost all (>99 percent) of the influenza viruses tested this season are susceptible to the four FDA-approved influenza antiviral medications recommended for use in the U.S. this season.
Nationally influenza B/Victoria viruses have been reported more frequently than other influenza viruses this season followed by A(H1N1)pdm09. The predominant virus varies by region. Regional and state level data about circulating influenza viruses can be found on FluView Interactive. The predominant virus also varies by age group.
Nationally, influenza B/Victoria viruses are the most commonly reported influenza viruses among children age 0-4 years (46 percent of reported viruses) and 5-24 years (58 percent of reported viruses), while A(H1N1)pdm09 viruses are the most commonly reported influenza viruses among persons 25-64 years (45 percent of reported viruses) and 65 years of age and older (48 percent of reported viruses).