National Center for Immunization and Respiratory Diseases (U.S.). Influenza Division.

Disease Outbreaks

Influenza, Human/epidemiology

Public Health Surveillance

All data are preliminary and may change as more reports are received.

During week 19 (May 6-12, 2018), influenza activity continued to decrease in the United States.

• Viral Surveillance: Overall, influenza A(H3) viruses have predominated this season. Since early March, influenza B viruses have been more frequently reported than influenza A viruses. The percentage of respiratory specimens testing positive for influenza in clinical laboratories decreased.

• 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.

• Influenza-associated Hospitalizations: A cumulative rate of 106.6 laboratory-confirmed influenza-associated hospitalizations per 100,000 population was reported.

• Outpatient Illness Surveillance: The proportion of outpatient visits for influenza-like illness (ILI) was 1.2%, which is below the national baseline of 2.2%. All 10 regions reported ILI below region-specific baseline levels. New York City, the District of Columbia, Puerto Rico and all 50 states experienced minimal ILI activity.

• Geographic Spread of Influenza: The geographic spread of influenza in two states was reported as widespread; Guam, Puerto Rico and three states reported regional activity; nine states reported local activity; the District of Columbia, the U.S. Virgin Islands and 33 states reported sporadic activity; and three states reported no influenza activity.

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