Outpatient visits for flu-like illness dropped for a second week in a row but remained above the peak seen during many flu seasons, federal officials say. They predict that flu activity is likely to remain elevated for several weeks.
During the week ending February 17—week 7 of this flu season—the proportion of outpatient visits for influenza-like illness (ILI) was 6.4%, down from the week 5 high of 7.5%, according to the Centers for Disease Control and Prevention (CDC). ILI has been at or above the national baseline for 13 weeks. Over the past five seasons, on average, ILI has remained at or above baseline for 16 weeks.
ILI activity was high in 39 states, moderate in five (Connecticut, Hawaii, Iowa, Utah, and Wisconsin), low in three (Florida, Idaho, and Washington), and minimal in three (Maine, Montana, and North Dakota). The geographic spread of influenza in Puerto Rico and 48 states was reported as widespread; the District of Columbia, Hawaii, and Oregon reported local activity.
Based on the most recent mortality data available (which lag behind other indicators), 9.5% of the deaths occurring during the week ending February 3 (week 5) were due to pneumonia and influenza. That’s a slight dip from a high of 10.6% reported in week 3.
Thirteen more flu-associated pediatric deaths were reported during the week, but several occurred weeks earlier. The total number of flu-related pediatric deaths reported this season now stands at 97. All but five of the latest reports were linked to influenza A strains.
The overall hospitalization rate is higher than the end-of-season rate for 2014–2015, a high-severity, H3N2-predominant season. The cumulative rate of confirmed flu-associated hospitalizations reached 74.5 per 100,000 population. Hospitalization remained highest among adults 65 years of age and older (322.7 per 100,000 population), adults 50–64 (79.9 per 100,000 population), and children 4 years of age and younger (52.6 per 100,000 population).
Among the hospitalizations, 83.4% were associated with influenza A virus. The most frequently identified flu virus subtype reported by public health laboratories during week 7 was influenza A(H3), but the proportion of influenza B has been rising. The total number of positive test results fell.
The CDC continues to recommend flu vaccination for all persons 6 months of age and older because flu viruses are likely to continue circulating for weeks and an increasing proportion of influenza B and H1N1 viruses are being detected.
Source: FDA; February 23, 2018.