Although the level of influenza across the United States continues to wind down, in some places influenza lingers on, with widespread influenza activity still reported by nine states (Connecticut, Indiana, Maine, Massachusetts, New Hampshire, New Jersey, New York, Oklahoma, and Vermont).
Influenza B, as we often see, is making a late season surge – and unlike with the mismatched H3N2 component of this year’s vaccine – the B (trivalent & quadrivalent) vaccine components appear a good match.
Roughly 2/3rds of the B viruses in circulation are covered by this year’s trivalent vaccine. Seven additional pediatric deaths were announced, and the 120 city P&I (Pneumonia & Influenza) mortality rate crept up slightly over the previous week.
Between seeing a flu season heavily dominated by H3N2 – which often affects the elderly more severely than H1N1 – and a greatly reduced Flu Vaccine Effectiveness (VE) due to the `drifted’ H3N2 virus, this has been a particularly harsh flu season for those over the age of 65.
A few excerpts from today’s report follow:
All data are preliminary and may change as more reports are received.
During week 9 (March 1-7, 2015), influenza activity continued to decrease, but remained elevated in the United States.
- Viral Surveillance: Of 14,634 specimens tested and reported by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories during week 9, 1,670 (11.4%) were positive for influenza.
- Pneumonia and Influenza Mortality: The proportion of deaths attributed to pneumonia and influenza (P&I) was above the epidemic threshold.
- Influenza-associated Pediatric Deaths: Seven influenza-associated pediatric deaths were reported.
- Influenza-associated Hospitalizations: A cumulative rate for the season of 55.7 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 2.4%, above the national baseline of 2.0%. Eight regions reported ILI at or above region-specific baseline levels. Puerto Rico and six states experienced high ILI activity; one state experienced moderate ILI activity; 13 states experienced low ILI activity; New York City and 30 states experienced minimal ILI activity; and the District of Columbia had insufficient data.
- Geographic Spread of Influenza: The geographic spread of influenza in nine states was reported as widespread; Guam, Puerto Rico, the U.S. Virgin Islands, and 29 states reported regional activity; 11 states reported local activity; and the District of Columbia and one state reported sporadic activity.