Although the news has focused heavily on COVID-19, flu season continues with a high level of activity and higher hospitalization rates among children and young adults than at this time in recent seasons, according to the Centers for Disease Control and Prevention (CDC) in the February 8, 2020 surveillance report.1
The CDC estimates 26 million flu illnesses, 250,000 hospitalizations and 14,000 deaths from flu so far this season. Hospitalization rates, overall, are similar to this time during recent seasons, but rates among children and young adults are higher at this time than recent seasons.
Influenza B was the predominant virus across all age groups earlier in the season, but over the past few weeks, influenza A(H1N1)pdm09 has become more dominant. For the season overall, influenza B viruses are the most commonly reported influenza viruses among children aged 0 to 4 years (56% of reported cases) and children and adolescents aged 5 to 24 years (70% of reported cases). Patients aged younger than 25 years provided roughly half of all the influenza positive specimens reported from public health laboratories.
Using the US Outpatient Influenza-like Illness Surveillance Network to determine activity, the CDC found a high level of influenza in nearly all states and territories during week 6:
- High – New York City, Puerto Rico, and 44 states
- Moderate – two states (Nevada and Oregon)
- Low – the District of Columbia and two states (Alaska and Florida)
- Minimal - one state (Idaho)
- Insufficient data to calculate from U.S. Virgin Islands and one state (Delaware)
Hospitalizations and deaths in pediatric population
The overall cumulative hospitalization rate is 41.9 per 100,000 population, similar to trends in previous flu seasons. However, the CDC reports that hospitalization rates for children and young adults are higher at this point in the season than at this time in recent seasons.
Per 100,000 population, the hospitalization rate is 65.9 in children aged 0 to 4 years and 17.3 in children and adolescents aged 5 to 17 years. Among 333 hospitalized children with information available on underlying medical conditions, 46.2% had at least 1 underlying medical condition (most commonly asthma).
So far this season, 92 pediatric influenza deaths have been reported. Roughly two-thirds of the deaths were linked to influenza B viruses, with 10 cases having lineage determined, all B/Victoria viruses. Thirty deaths were associated with influenza A viruses. Eighteen were subtyped, with 17 found to be A(H1N1)pdm09 and one A(H3).
1. Centers for Disease Control and Prevention (CDC). Weekly U.S. Influenza Surveillance Report. Key updates for Week 6, ending February 8, 2020. CDC website. Available at: https://www.cdc.gov/flu/weekly/index.htm. Updated February 8, 2020. Accessed February 19, 2020.