Weekly U.S. Influenza Surveillance Report

According to this week's FluView report (Jan 27- Feb 2), seasonal flu activity increased in the United States. New York City and 24 states experienced high influenza-like illness (ILI) activity. CDC estimates that since October 1, 2018, there have been 13.2 million – 15.2 million flu illnesses, 6.2 million – 7.2 million flu medical visits, and 155,000 – 186,000 flu hospitalizations this season.

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2018-2019 Influenza Season Week 5 ending February 2, 2019

Synopsis:

Influenza activity increased in the United States. Influenza A(H1N1)pdm09, influenza A(H3N2), and influenza B viruses continue to co-circulate. Below is a summary of the key influenza indicators for the week ending February 2, 2019

Viral Surveillance:The percentage of respiratory specimens testing positive for influenza viruses in clinical laboratories increased. Influenza A viruses have predominated in the United States since the beginning of October. Influenza A(H1N1)pdm09 viruses have predominated in most areas of the country, however influenza A(H3) viruses have predominated in the southeastern United States (HHS Region 4).

Virus Characterization:The majority of influenza viruses characterized antigenically and genetically are similar to the cell-grown reference viruses representing the 2018–2019 Northern Hemisphere influenza vaccine viruses.
Antiviral Resistance:The vast majority of influenza viruses tested (>99%) show susceptibility to oseltamivir and peramivir. All influenza viruses tested showed susceptibility to zanamivir.

Influenza-like Illness Surveillance:The proportion of outpatient visits for influenza-like illness (ILI) increased to 4.3%, which is above the national baseline of 2.2%. All 10 regions reported ILI at or above their region-specific baseline level.

ILI State Activity Indictor Map: New York City and 24 states experienced high ILI activity; Puerto Rico and 10 states experienced moderate ILI activity; the District of Columbia and 13 states experienced low ILI activity; and three states experienced minimal ILI activity.

Geographic Spread of Influenza: The geographic spread of influenza in Puerto Rico and 47 states was reported as widespread; two states reported regional activity; the District of Columbia and one state reported local activity; the U.S. Virgin Islands reported sporadic activity; and Guam did not report.
Influenza-associated Hospitalizations A cumulative rate of 20.1 laboratory-confirmed influenza-associated hospitalizations per 100,000 population was reported. The highest hospitalization rate is among adults 65 years and older (53.0 hospitalizations per 100,000 population).
Pneumonia and Influenza Mortality: The proportion of deaths attributed to pneumonia and influenza (P&I) was below the system-specific epidemic threshold in the National Center for Health Statistics (NCHS) Mortality Surveillance System.
Influenza-associated Pediatric Deaths: Four influenza-associated pediatric deaths were reported to CDC during week 5.