Seasonal flu activity in the US significantly increased during the final week of 2019 and is expected to keep rising.
Nearly 7% of all outpatient visits to healthcare providers in the final week of 2019 were for influenza-like illness (ILI), marking the 8th consecutive week where ILI activity in the US was at or above the national baseline of 2.4%, according to the recent US Centers for Disease Control and Prevention (CDC) FluView report.
This is an increase from the previous week (ie, week 51) when 5.1% of outpatient visits were for ILI. This rise, however, “may be influenced in part by a reduction in routine healthcare visits surrounding the holidays occurring during week 52 as has occurred during previous seasons,” the CDC noted in the report.
The number of states that experienced high ILI activity increased from 28 the previous week to 37 by the end of week 52; Delaware and Idaho were the only 2 states with minimal ILI activity.
The report also highlighted the increase in overall influenza-associated hospitalization rate from 7.8 per 100 000 population in week 51 to 9.2 per 100 000 population in week 52, which is fairly typical at this time during the season.
Adults aged ≥65 years had the highest rate of hospitalizations (19.9 per 100 000 population), followed by children aged 0-4 years (17.8 per 100 000 population) and adults aged 50-64 years (10 per 100 000 population).
The CDC also reported that the percentage of respiratory specimens that tested positive for influenza rose to 26.3% in week 52, with the majority of positive specimens (67.9%) being influenza B which is uncommon for this time of year.
During the last week of 2019, 5 new influenza-associated pediatric deaths were reported as well, bringing the total to 27 such deaths for the season. Among these deaths, 18 were associated with influenza B and 9 were linked to influenza A.
Overall, the CDC estimates there have been approximately 6.4 million flu illnesses, 55 000 hospitalizations, and 2900 flu-related deaths since the start of the 2019-2020 season.