Influenza activity decreased in the United States during the week ending February 24, according to the Centers for Disease Control and Prevention (CDC).
In week 8 of this trying flu season, the proportion of outpatient visits to doctors blamed on influenza-like illness (ILI) fell for the third straight week to 5.0% from a high of 7.5% in week 5. Still, flu-related doctor visits remained elevated for the 14th week in a row.
The CDC said 9.0% of the deaths occurring during the week ending February 10 (week 6) were due to pneumonia and Influenza, continuing a gradual decrease from a high of 10.6% reported in week 3. Mortality data lags behind other flu reports.
Seventeen more flu-related pediatric deaths were reported in week 8 (though several occurred earlier), bringing the season’s total to 114. Nine were linked with influenza B variants and the rest with influenza A.
The cumulative rate of laboratory-confirmed, flu-associated hospitalizations has reached 81.7 per 100,000 population, with the rate remaining highest among adults ages 65 years and older, adults ages 50–64, and children younger than 4 years of age.
Among the hospitalizations, 81.6% were linked to influenza A virus, and 67.2% of hospitalized adults had at least one reported underlying medical condition—most commonly cardiovascular disease, metabolic disorder, obesity, and chronic lung disease. Among hospitalized children, 44.2% had at least one underlying medical condition, often asthma, a neurological disorder, or obesity.
The number of states reporting high ILI activity fell to 32 from 39 a week earlier as the flu’s impact continued to ease in the West, with ILI activity moderate in nine states (California, Connecticut, Delaware, Nevada, Ohio, Oregon, Utah, West Virginia, and Wisconsin), low in six states (Hawaii, Idaho, Iowa, North Dakota, Tennessee, and Washington), and minimal in three (Florida, Maine, and Montana).
The geographic spread of influenza was reported as widespread in 45 states, down from 48 the week before. Only regional activity was reported by Minnesota and Texas and only local activity was reported by the District of Columbia, Hawaii, Oregon, and Vermont.
Influenza A(H3) viruses continue to be predominant this season. However, during week 8 the overall proportion of influenza A viruses declined and the proportion of influenza B viruses increased. The percentage of respiratory specimens testing positive for influenza in clinical laboratories decreased.
Source: CDC; March 2, 2018.