Friday, January 19, 2018

CDC FluView Week #2 - Flu Still Rising


Although there were hopes expressed last week that influenza was beginning to plateau across the nation, today's FluView report shows another hefty increase in outpatient visits for ILI (Influenza-like Illness), and cumulative hospitalizations (all ages) have jumped by nearly 50% (22.7 to 31.5) since last week.

Last week the P&I mortality rate (which lags other data) was at the epidemic threshold of 7.0% for week 51, while this weeks report has it at 8.2% (see below) - well above the epidemic threshold of 7.1% for week 52.

P&I Mortality is a notoriously trailing indicator, and these numbers are subject to revision,  as severely ill patients may survive for days or weeks before succumbing and there are often delays in reporting adult flu deaths.

Sadly, another 10 pediatric flu deaths are reported for week 2. While nationally reportable, these numbers likely only capture 1/2 to 1/3rd of the pediatric flu deaths each year, and we often see belated reporting in this category as well.

 This week's summary from a much longer, and far more detailed report:
2017-2018 Influenza Season Week 2 ending January 13, 2018

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

During week 2 (January 7-13, 2018), influenza activity increased in the United States.
  • Viral Surveillance: The most frequently identified influenza virus subtype reported by public health laboratories during week 2 was influenza A(H3). The percentage of respiratory specimens testing positive for influenza in clinical laboratories increased.
  • Pneumonia and Influenza Mortality: The proportion of deaths attributed to pneumonia and influenza (P&I) was above the system-specific epidemic threshold in the National Center for Health Statistics (NCHS) Mortality Surveillance System.
  • Influenza-associated Pediatric Deaths: Ten influenza-associated pediatric deaths were reported
  • Influenza-associated Hospitalizations: A cumulative rate of 31.5 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 6.3%, which is above the national baseline of 2.2%. All 10 regions reported ILI at or above region-specific baseline levels. New York City, Puerto Rico, and 32 states experienced high ILI activity; 9 states experienced moderate ILI activity; the District of Columbia and six 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 49 states was reported as widespread; Guam reported regional activity; the District of Columbia and one state reported local activity; and the U.S. Virgin Islands reported sporadic activity.

There are reports from some parts of the country that the intensity of flu may be starting to wane.  Even so, there is like another 6 to 10 weeks of flu activity ahead, and the potential for seeing a `second wave' of influenza B or H1N1 later in the spring.

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