We’ve the final FluView report of 2014, and while surveillance and reporting over the holidays often suffers (or is at least delayed), there’s little doubt that influenza continues to rise and spread across the nation. Roughly 30% of samples tested by the CDC in week 52 tested positive for influenza – up from 17% positive rate at the start of December.
And as has been the case since the flu season kicked off, samples have been overwhelmingly Influenza A, and of those, almost all H3N2.
The percentage of `drifted’ H3N2 viruses detected – those that differ antigenically from this year’s vaccine – remains roughly 70% (22 of 29 samples tested this week). Despite the expected reduced effectiveness of this year’s flu shot, the CDC advises there are still benefits to getting the vaccine if you haven’t done so already.
- There are two other strains (H1N1 & Influenza B) covered by the shot, which may emerge later in the year
- 30% the H3N2 viruses tested so far are still a `match’ to the vaccine strain
- There may still be some degree of cross-protection afforded against this new strain.
There were, regrettably, 6 influenza related pediatric deaths reported this week.
The slight `good news’ in this week’s report is that the P&I weekly mortality numbers have softened slightly, dropping below the `epidemic threshold’ set just last week. But given that Pneumonia & Influenza Mortality reporting is usually a `lagging indicator’, and the holidays often impede the flow of reporting, one shouldn’t read too much into this minor drop.
Some excerpts from today’s report.
All data are preliminary and may change as more reports are received.
During week 52 (December 21-27, 2014), influenza activity continued to increase in the United States.
- Viral Surveillance: Of 24,001 specimens tested and reported by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories during week 52, 7,289 (30.4%) 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: Six influenza-associated pediatric deaths were reported.
- Influenza-associated Hospitalizations: A cumulative rate for the season of 12.6 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 5.9%, above the national baseline of 2.0%. All 10 regions reported ILI at or above region-specific baseline levels. Puerto Rico and 29 states experienced high ILI activity; New York City and six states experienced moderate ILI activity; five states experienced low ILI activity; nine states experienced minimal ILI activity; and the District of Columbia and one state had insufficient data.
- Geographic Spread of Influenza: The geographic spread of influenza in 43 states was reported as widespread; Puerto Rico and six states reported regional activity; one state reported sporadic activity; and the District of Columbia, Guam, and the U.S. Virgin Islands did not report.
Influenza Virus Characterization*:
CDC has characterized 334 influenza viruses [10 A(H1N1)pdm09, 268 A(H3N2), and 56 influenza B viruses] collected by U.S. laboratories since October 1, 2014.
Influenza A Virus 
- A (H1N1)pdm09 : All 10 H1N1 viruses tested were characterized as A/California/7/2009-like, the influenza A (H1N1) component of the 2014-2015 Northern Hemisphere influenza vaccine.
- A (H3N2) : Eighty-five (31.7%) of the 268 H3N2 viruses tested have been characterized as A/Texas/50/2012-like, the influenza A (H3N2) component of the 2014-2015 Northern Hemisphere influenza vaccine. One hundred eighty-three (68.3%) of the 268 viruses tested showed either reduced titers with antiserum produced against A/Texas/50/2012 or belonged to a genetic group that typically shows reduced titers to A/Texas/50/2012. Among viruses that showed reduced titers with antiserum raised against A/Texas/50/2012, most were antigenically similar to A/Switzerland/9715293/2013, the H3N2 virus selected for the 2015 Southern Hemisphere influenza vaccine. A/Switzerland/9715293/2013 is related to, but antigenically and genetically distinguishable, from the A/Texas/50/2012 vaccine virus. A/Switzerland-like H3N2 viruses were first detected in the United States in small numbers in March of 2014 and began to increase through the spring and summer.
Influenza B Virus 
Thirty-nine (70%) of the influenza B viruses tested belong to B/Yamagata/16/88 lineage and the remaining 17 (30%) influenza B viruses tested belong to B/Victoria/02/87 lineage.
- Yamagata Lineage : All 39 B/Yamagata-lineage viruses were characterized as B/Massachusetts/2/2012-like, which is included as an influenza B component of the 2014-2015 Northern Hemisphere trivalent and quadrivalent influenza vaccines.
- Victoria Lineage : Fifteen (88%) of the 17 B/Victoria-lineage viruses were characterized as B/Brisbane/60/2008-like, the virus that is included as an influenza B component of the 2014-2015 Northern Hemisphere quadrivalent influenza vaccine. Two (12%) of the B/Victoria-lineage viruses tested showed reduced titers to B/Brisbane/60/2008.
During week 52, 6.8% of all deaths reported through the 122 Cities Mortality Reporting System were due to P&I. This percentage was below the epidemic threshold of 6.9% for week 52.
Six influenza-associated pediatric deaths were reported to CDC during week 52. Three deaths were associated with an influenza A (H3) virus and occurred during weeks 51 and 52 (weeks ending December 20 and December 27, 2014, respectively). Two deaths were associated with an influenza A virus for which no subtyping was performed and occurred during weeks 51 and 52. One death was associated with an influenza virus for which the type was not determined and occurred during week 51.
A total of 21 influenza-associated deaths have been reported during the 2014-2015 season from 11 states (Arizona , Colorado , Florida , Kansas , Minnesota , North Carolina , Nevada , Ohio , Tennessee , Texas , and Virginia ).
Additional data can be found at: http://gis.cdc.gov/GRASP/Fluview/PedFluDeath.html.
Whether you got the shot or not, with people returning back to work and to school after the holidays, it is important to focus on on practicing good flu hygiene. The CDC suggests:
- Try to avoid close contact with sick people.
- If you are sick with flu-like illness, CDC recommends that you stay home for at least 24 hours after your fever is gone except to get medical care or for other necessities. (Your fever should be gone without the use of a fever-reducing medicine.)
- While sick, limit contact with others as much as possible to keep from infecting them.
- Cover your nose and mouth with a tissue when you cough or sneeze. Throw the tissue in the trash after you use it.
- Wash your hands often with soap and water. If soap and water are not available, use an alcohol-based hand rub.
- Avoid touching your eyes, nose and mouth. Germs spread this way.
- Clean and disinfect surfaces and objects that may be contaminated with germs like the flu.