Flu Season Continues to Worsen, CDC Reports

32 states experience high activity levels in week ending January 13

A U.S. map of flu activity issued Friday by the Centers for Disease Control and Prevention (CDC) was a sea of red: the color marking the highest levels of outpatient visits for an illness that continues to worsen this season.

According to this week's CDC report, covering the week of January 7 to 13, 32 states and Puerto Rico experienced high influenza-like illness (ILI) activity levels. Nine states experienced moderate activity. The geographic reach of the flu in 49 states and Puerto Rico was reported as widespread.

The most frequently identified influenza virus subtype reported by public health laboratories during the week was influenza A(H3). The H3N2 subtype has accounted for 78% of the positive flu specimens tested since October 1, 2017, the latest report said.

Based on the latest available mortality surveillance data, 8.2% of the deaths that occurred during the week ending December 30, 2017, were due to pneumonia and influenza—a percentage that is above the epidemic threshold of 7.1% for the week. Although reporting is not yet complete, the CDC has so far recorded 453 influenza deaths and 2,893 pneumonia deaths for the final week of 2017.

Ten influenza-associated pediatric deaths were reported in the week ending January 13, several of which occurred earlier in the flu season. Seven of the 10 were related to influenza A viruses. Since the flu season began last October, the flu has claimed the lives of 30 children, the CDC reports.

A total of 8,990 laboratory-confirmed influenza-associated hospitalizations were reported between October 1, 2017, and January 13, 2018. The cumulative rate is 31.5 laboratory-confirmed influenza-associated hospitalizations per 100,000 population.

The proportion of outpatient visits for ILI was 6.3%, well above the national baseline of 2.2%. All 10 regions of the U.S. reported ILI at or above region-specific baseline levels. New York City, Puerto Rico, and 32 states experienced high ILI activity; nine states experienced moderate ILI activity; and the District of Columbia and six states (Connecticut, Michigan, New Hampshire, Utah, Vermont, and Washington) experienced low ILI activity. Only three states experienced minimal ILI activity: Montana, Maine, and Delaware.

The CDC’s map of outpatient ILI visits tells the story: the southern two-thirds of the country is awash in red, signaling the highest ILI activity (broken only by a streak of still-high orange for Florida), while ILI activity is at least slightly lower in a strip of northernmost states from Washington state to Maine.

Source: CDC; January 19, 2018.