Flu activity continues to decline and is below national baseline levels. However, activity remains elevated in parts of the northeast. While most flu activity occurs from October to May in the United States, flu viruses are detected year-round, including at lower levels during the spring and summer months.
H3N2 viruses predominated earlier in the season, however, influenza B viruses have been more common in recent weeks. This season has been severe for people 65 years and older, with very high hospitalization rates being recorded.
Influenza antiviral drugs can treat flu illness. CDC recommends these drugs be used to treat people who are very sick or who are at high risk of serious flu-related complications who have flu symptoms. Early antiviral treatment works best.
2014-2015 Influenza Season Week 19 ending May 16, 2015
During week 19 (May 10-16, 2015), influenza activity continued to decrease in the United States.
- Viral Surveillance: Of 6,553 specimens tested and reported by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories during week 19, 228 (3.5%) were positive for influenza.
- Pneumonia and Influenza Mortality: The proportion of deaths attributed to pneumonia and influenza (P&I) was below the epidemic threshold.
- Influenza-associated Pediatric Deaths: Three influenza-associated pediatric deaths were reported, including two influenza-associated pediatric deaths that occurred during the 2013-14 season.
- Influenza-associated Hospitalizations: A cumulative rate for the season of 65.5 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 1.3%, which is below the national baseline of 2.0%. All 10 regions reported ILI below region-specific baseline levels. Puerto Rico and one state experienced low ILI activity; New York City and 49 states experienced minimal ILI activity; and the District of Columbia had insufficient data.
- Geographic Spread of Influenza: The geographic spread of influenza in one state was reported as widespread; Guam and one state reported regional activity; Puerto Rico and nine states reported local activity; the District of Columbia and 31 states reported sporadic activity; and the U.S. Virgin Islands and eight states reported no influenza activity.