Influenza activity dropped during the week ending Feb. 15, according to the Centers for Disease Control and Prevention. That decline, along with revised data from the 2 previous weeks, suggests that the 2019-2020 season has peaked for the second time. The rate of outpatient visits for influenza-like illness (ILI) came in at 6.1% for the week ending Feb. 15, after two straight weeks at 6.7%, the CDC’s influenza division reported Feb. 21.
The rates for those 2 earlier weeks had previously been reported at 6.8% (Feb. 8) and 6.6% (Feb. 1), which means that there have now been 2 consecutive weeks without an increase in national ILI activity.
State-level activity was down slightly as well. For the week ending Feb. 15, there were 39 states and Puerto Rico at the highest level of activity on the CDC’s 1-10 scale, compared with 41 states and Puerto Rico the week before. The number of states in the “high” range, which includes levels 8 and 9, went from 44 to 45, however, CDC data show.
Laboratory measures also dropped a bit. For the week, 29.6% of respiratory specimens tested positive for influenza, compared with 30.3% the previous week. The predominance of influenza A continued to increase, as type A went from 59.4% to 63.5% of positive specimens and type B dropped from 40.6% to 36.5%, the influenza division said.
In a separate report, the CDC announced interim flu vaccine effectiveness estimates.For the 2019-2020 season so far, “flu vaccines are reducing doctor’s visits for flu illness by almost half (45%). This is consistent with estimates of flu vaccine effectiveness (VE) from previous flu seasons that ranged from 40% to 60% when flu vaccine viruses were similar to circulating influenza viruses,” the CDC said.
Although VE among children aged 6 months to 17 years is even higher, at 55%, this season “has been especially bad for children. Flu hospitalization rates among children are higher than at this time in other recent seasons, including the 2017-18 season,” the CDC noted.
The number of pediatric flu deaths for 2019-2020 – now up to 105 – is “higher for the same time period than in every season since reporting began in 2004-05, with the exception of the 2009 pandemic,” the CDC added.
Interim VE estimates for other age groups are 25% for adults aged 18-49 and 43% for those 50 years and older. “The lower VE point estimates observed among adults 18-49 years appear to be associated with a trend suggesting lower VE in this age group against A(H1N1)pdm09 viruses,” the CDC said.