Approximately half of jurisdictions in the United States now report high or moderate influenza activity; at this time last year, only four states had done so. Influenza activity continued to vary in different areas of the United States during the week ending November 30 (week 48), with southern states particularly hard hit, according to the CDC.
Several influenza indicators are at or above levels 3 weeks earlier than they were last influenza season. The percentage of outpatients seeking healthcare for influenzalike symptoms during week 48 was 3.5% and has now been above the baseline of 2.4% for 4 weeks.
Last season at this time, that percentage exceeded the baseline at 2.3% during week 47 but remained below 3% until week 51, when it rose to 3.3%. The baseline last season was 2.2%.
A total of 26,576 specimens were tested in clinical laboratories during week 48; of those, 2713 (10.2%) were positive for influenza. That’s an increase from week 47, when 1702 (8.0%) of 21,367 specimens were positive for influenza.
Predominant Strain Different
This season, the predominant viral strain differs from that which began the 2018–2019 season. Nationally, B/Victoria now predominates, followed by A(H1N1)pdm09 and A(H3N2).
Last season at this time, influenza A(H1N1)pdm09, influenza A(H3N2), and influenza B viruses co-circulated; however, influenza A(H1N1)pdm09 viruses have been predominant since late September 2018. Influenza B viruses became predominant later in the season.
Thirteen jurisdictions (Puerto Rico, Alabama, Georgia, Louisiana, Minnesota, Mississippi, Nebraska, Nevada, New Mexico, South Carolina, Tennessee, Texas, and Washington) reported high influenza activity during the week that ended November 30, up from eight the week before.
Fifteen jurisdictions (New York City, Arizona, Arkansas, Colorado, Connecticut, Florida, Hawaii, Kentucky, Maryland, Missouri, New Jersey, North Dakota, Oklahoma, Utah, and Virginia) reported moderate activity, an increase from seven the week before.
The District of Columbia and eight states reported low influenza activity, and 16 states reported minimal activity. There were insufficient data to determine an activity level for the US Virgin Islands.
Deaths from pneumonia and influenza are still below threshold this season, at 4.8% (the threshold is 6.4%). One pediatric death was reported; there have been a total of six this season.
Approximately Half of US Currently Affected
Geographically, influenza is widespread in 16 states (Alabama, California, Connecticut, Georgia, Indiana, Louisiana, Massachusetts, Mississippi, Nevada, New Mexico, New York, Pennsylvania, South Carolina, Tennessee, Texas, and Virginia).
The flu is regional in Puerto Rico and 14 states (Alaska, Arizona, Colorado, Florida, Idaho, Kentucky, Minnesota, Montana, Nebraska, Oklahoma, Oregon, Utah, Washington, and Wisconsin).
Last season at this time, influenza was widespread in only Minnesota and was regional in nine states.
Influenza is local in 17 states (Arkansas, Delaware, Hawaii, Illinois, Iowa, Maine, Maryland, Michigan, Missouri, New Hampshire, New Jersey, North Carolina, North Dakota, Ohio, South Dakota, Vermont, and Wyoming) and sporadic in the District of Columbia, the US Virgin Islands, Kansas, Rhode Island, and West Virginia.
There were 784 laboratory-confirmed influenza hospitalizations reported between October 1, 2019, and November 30, 2019. The overall hospitalization rate was 2.7 per 100,000 population, with the highest rates among adults aged 65 years or older (7.0 per 100,000 population), followed by children aged 0 to 4 years (4.6 per 100,000 population) and adults aged 50 to 64 years (2.7 per 100,000 population).
The CDC stresses that it is not too late to get vaccinated against influenza.
CDC. Weekly US Influenza Surveillance Report, updates for week 48. Full text