#15,427
Although the memory of last year's (2019-2020) flu season has been largely pushed aside by the emergence of our COVID-19 pandemic in February and March - back in January of this year - we were embroiled in a moderately severe H1N1/Influenza B Victoria epidemic.
Unlike H3N2 dominated flu seasons - which generally takes its greatest toll on the elderly - both H1N1 and Influenza B tend to hit young adults and children the hardest.
On January 10th, 2020 the CDC issued a HAN Advisory and a FluView report warning of elevated flu activity, and its impact on children.
Elevated Influenza Activity: Influenza B/Victoria and A(H1N1)pdm09 Viruses are the Predominant Viruses
The Centers for Disease Control and Prevention reminds clinicians that influenza B viruses can cause severe illness in people of all ages, including children. CDC continues to recommend influenza vaccination and prompt antiviral treatment of high-risk outpatients and hospitalized patients with suspected influenza.
On that date, the CDC's FluView reported:
Influenza-Associated Pediatric Mortality
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.
- 21 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.
Only a decade ago, Influenza B was viewed generally as a `less serious' infection than influenza A - affecting mainly children - and producing relatively mild illness in adults. But as the above report illustrates, nearly twice as many children had died from influenza B than from H1N1 by early January.
A study, published in 2014 in the Clinical Infectious Diseases Journal, challenged the old ideas about influenza B.
Comparing Clinical Characteristics Between Hospitalized Adults With Laboratory-Confirmed Influenza A and B Virus Infection
Su Su Sandra S. Chaves Alejandro Perez Tiffany D'Mello Pam D. Kirley Kimberly Yousey-Hindes Monica M. Farley Meghan Harris Ruta Sharangpani Ruth Lynfield ...
Clinical Infectious Diseases, Volume 59, Issue 2, 15 July 2014, Pages 252–255,
https://doi.org/10.1093/cid/ciu269 Published: 18 April 2014
ABSTRACT
We challenge the notion that influenza B is milder than influenza A by finding similar clinical characteristics between hospitalized adult influenza-cases. Among patients treated with oseltamivir, length of stay and mortality did not differ by type of virus infection.
The CDC, which partnered in this study, published the following summary:
New CDC Study Compares Severity of Illness Caused by Flu A and B Viruses
Influenza B virus infections can be just as severe as influenza A virus infections
As late-season influenza B viruses currently predominate in the United States, a new study published by CDC and partners highlights the comparative severity of illness associated with influenza A versus influenza B virus infections. The results of the study showed that among hospitalized adults, flu B viruses caused equally severe disease outcomes and clinical characteristics as flu A viruses.
This contradicts a common misconception that flu B viruses are associated with milder disease than flu A viruses.
While the 2019-2020 flu season doesn't end until the end of September, yesterday's FluView report contained a grim milestone; the announcement of the 188th pediatric flu-related death of the year, matching the record number set during the severe 2017-2018 flu season.
Although pediatric flu deaths have been a `reportable' disease by the CDC since 2004, it is estimated that only between 1/3rd and 1/4th of all pediatric flu deaths are captured by surveillance. Which means the true toll this year could be substantially higher.
In the aftermath of the H1N1 pandemic of 2009, the CDC estimated that the likely number of pediatric deaths in the United States ranged from 910 to 1880, or anywhere from 3 to 6 times higher than reported.
Whether you are talking about COVID-19, influenza, or any other infectious disease - it is safe to assume that surveillance and reporting always under-represents the true burden of a disease (see 2018's Why Flu Fatality Numbers Are So Hard To Determine).
The CDC issued the following press release on yesterday's announcement:
2019-20 Season’s Pediatric Flu Deaths Tie High Mark Set During 2017-18 Season
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August 21, 2020 – CDC today reported one new seasonal flu-related death in a child that occurred during the 2019-2020 season, bringing the total number of flu deaths in children reported to CDC for last season to 188. This matches the highest recorded number for pediatric flu deaths reported during a regular flu season, which occurred during the 2017-2018 flu season.
Among the 188 reported pediatric flu deaths:This tragic milestone underscores how serious flu can be and serves as a reminder of the importance of an annual flu vaccine. In 2019-2020, only 21 percent of children eligible for vaccination were fully vaccinated against flu. This percentage was similar to past seasons.
- 43% (81) occurred in children younger than 5 years old
- 12 occurred in children younger than 6 months and thus too young to get a flu vaccine
- 57% (107) deaths occurred in children 5-17 years old
- Of the 175 pediatric deaths among children with known information on medical conditions, 76 (43.4%) had a pre-existing medical condition.
- Nearly two-thirds of the deaths were attributed to influenza B infections.
CDC recommends everyone 6 months and older get an annual flu vaccine, especially children who are younger than 5 years of age or children of any age who have a high risk medical condition, because they are more likely to develop serious flu complications that can lead to hospitalization and death. Getting vaccinated has been shown to reduce flu illnesses, doctor’s visits, missed school days, and reduce the risk of flu-related hospitalization and death in children.
Flu deaths in children have been nationally reportable since 2004. Since that time, flu-related deaths in children reported to CDC during regular flu seasons have ranged from 37 to 188 deaths. For comparison, during the 2009 H1N1 pandemic, from April 2009 to September 2010, 358 flu deaths in children were reported to CDC.
While any death in a child from a vaccine preventable illness is a tragedy, the number of pediatric flu deaths reported to CDC each season is likely an undercount. For example, even though the reported number of deaths during the 2017-2018 flu season was 188, CDC estimates the actual number was closer to 600. It is likely the actual number of children who died from flu during the 2019-2020 season is higher as well.
Children should be vaccinated every flu season for the best protection against flu. For children who will need two doses of flu vaccine, the first dose should be given as early in the season as possible. For other children, it is good practice to get them vaccinated by the end of October. However, getting vaccinated later can still be protective if flu viruses are still circulating.
In addition to getting a flu shot, children and caregivers of young children should take everyday preventive actions CDC recommends for everyone, including covering coughs, washing hands often, and avoiding people who are sick.
