CDC: Flu activity hits highest level this season

The percentage of people visiting the doctor for influenza-like illness (ILI) last week jumped from 3.8% to 4.3%, the highest of the 2018-19 flu season, according to today's weekly FluView update from the Centers for Disease Control and Prevention (CDC).

Though almost double the national baseline (2.2%), the ILI level is still much lower than last year's peak of 7.5%, the CDC said. For the fifth consecutive week, all 10 geographic regions in the United States reported ILI levels at or above region-specific baselines.

"For comparison purposes, over the past five flu seasons, the peak percent of visits due to ILI has ranged between 3.6% (2015-2016) and 7.5% (2017-2018)," the CDC said in its summary.

Severity indicators rise across nation

All severity indicators rose in the last week, and CDC said it expected flu activity to remain elevated for a number of weeks.

All 10 geographic regions of the country recorded high ILI activity, a measure of clinic visits for flu, for the fourth week of 2019.

New York City and 24 states reported high ILI, compared with 23 states the previous week. Puerto Rico and 10 states are experiencing moderate ILI, and the District of Columbia and 13 states are reporting low ILI. Only three states are reporting minimal ILI activity.

Widespread geographic influenza activity was reported in 47 states, up from 45 states in the previous week. Only West Virginia, Alaska, Hawaii, and the District of Columbia have regional or local flu activity.

Hospitalization rates lower than last season

The overall hospitalization rate last week for flu was 20.1 per 100,000 population, up from 15.3 per 100,000 population the week before. As has been the case all season, the highest hospitalization rate is among adults ages 65 years and older (53.0 per 100,000) followed by children younger than 5 years (33.5 per 100,000), and adults aged 50 to 64 years (27.2 per 100,000).

Last year, during week 5, the cumulative hospitalization rate was 65.5 per 100,000, and the CDC said that, over the last five flu seasons, cumulative end-of-season hospitalization rates have ranged from 35.1 per 100,000 (2013-14) to 102.9 per 100,000 (2017-18).

Four more pediatric deaths were recorded in the past week, bringing the season's total to 28. All 4 deaths were associated with influenza A viruses.

Influenza A still dominates this flu season, representing 98.3% of lab specimens tested. Rates of H3N2, the strain that has been dominant in the southeast, rose a bit last week. About one third of subtypes influenza A viruses (35%) were H3N2, and 65% were H1N1.

See also:

Feb 8 CDC situation summary

Feb 8 CDC FluView

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