Weekly U.S. Influenza Surveillance Report | CDC

Weekly U.S. Influenza Surveillance Report | CDC

Weekly U.S. Influenza Surveillance Report

According to this week's FluView report (May 12 - 18), seasonal flu activity remains low in the United States. This is the final full FluView for the 2018-2019 season. Several flu surveillance components operate year-round and an abbreviated FluView report will be published throughout the summer and early fall. The first FluView for the 2019-2020 season will be published on October 11, 2019.

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Synopsis:

Influenza activity remained low in United States and was similar to last week. While influenza A(H1N1)pdm09 viruses predominated from October to mid-February, influenza A(H3N2) viruses have been more commonly identified since late February. Small numbers of influenza B viruses also have been reported. Below is a summary of the key influenza indicators for the week ending May 18, 2019:

• Viral Surveillance:The percentage of respiratory specimens testing positive for influenza viruses in clinical laboratories remained low. During the most recent three weeks, influenza A(H3) viruses were reported more frequently than influenza A(H1N1)pdm09 viruses nationally.
• Virus Characterization:The majority of influenza A(H1N1)pdm09 and influenza B viruses characterized antigenically are similar to the cell-grown reference viruses representing the 2018–2019 Northern Hemisphere influenza vaccine viruses. However, the majority of influenza A(H3N2) viruses are antigenically distinguishable from A/Singapore/INFIMH-16-0019/2016 (3C.2a1), a cell-propagated reference virus representing the A(H3N2) component of  2018-19 Northern Hemisphere influenza vaccines.
• Antiviral Resistance:The vast majority of influenza viruses tested (>99%) show susceptibility to oseltamivir and peramivir. All influenza viruses tested showed susceptibility to zanamivir and baloxavir.
• Influenza-like Illness Surveillance:The proportion of outpatient visits for influenza-like illness (ILI) remained at 1.5%, which is below the national baseline of 2.2%. All regions reported ILI below their region-specific baseline level.
• ILI State Activity Indictor Map: Puerto Rico and two states experienced low ILI activity; and New York City, the District of Columbia, the U.S. Virgin Islands and 48 states experienced minimal ILI activity.
• Geographic Spread of Influenza: The geographic spread of influenza in one state was reported as widespread; Puerto Rico and one state reported regional activity; eight states reported local activity; the District of Columbia, the U.S. Virgin Islands and 36 states reported sporadic activity; four states reported no activity; and Guam did not report.
• Influenza-associated Hospitalizations A cumulative rate of 65.7 laboratory-confirmed influenza-associated hospitalizations per 100,000 population was reported. The highest hospitalization rate is among adults 65 years and older (221.7 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: Three influenza-associated pediatric deaths were reported to CDC during week 20. Two occurred during the 2018-2019 season and one occurred during the 2017-2018 season.