FluView Week 51
While avian flu in China and Egypt have captured a good deal of our attention, we continue to tread deeper into a difficult H3N2 dominated flu season, with increasing media reports of crowded hospitals and scattered deaths across the nation.
The new `drifted’ H3N2 virus – one that is a poor match for this year’s vaccine strain – continues to show up in surveillance, although unlike last week where all of the samples (n=12) were a `miss’, this week 14 of 30 H3N2 viruses tested match the vaccine. At this point in the season, roughly 2/3rds of the H3N2 viruses tested are of the new strain.
This week, for the first time in this year’s flu season, the P&I (Pneumonia & Influenza) Mortality level was at the epidemic threshold. Nearly all of the flu being reported is influenza A, and nearly all of those cases are H3N2, which often produces a more severe flu season than does H1N1.
Some excerpts from this weeks report include:
All data are preliminary and may change as more reports are received.
During week 51 (December 14-20, 2014), influenza activity continued to increase in the United States.
- Viral Surveillance: Of 21,858 specimens tested and reported by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories during week 51, 6,152 (28.1%) were positive for influenza.
- Pneumonia and Influenza Mortality: The proportion of deaths attributed to pneumonia and influenza (P&I) was at the epidemic threshold.
- Influenza-associated Pediatric Deaths: Four influenza-associated pediatric deaths were reported.
- Influenza-associated Hospitalizations: A cumulative rate for the season of 9.7 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 5.5%, above the national baseline of 2.0%. All 10 regions reported ILI at or above region-specific baseline levels. Puerto Rico and 22 states experienced high ILI activity; six states experienced moderate ILI activity; New York City and eight states experienced low ILI activity; 14 states experienced minimal ILI activity; and the District of Columbia had insufficient data.
- Geographic Spread of Influenza: The geographic spread of influenza in 36 states was reported as widespread; Guam, Puerto Rico, and 10 states reported regional activity; the District of Columbia, the U.S. Virgin Islands, and two states reported local activity; and two states reported sporadic activity.
Influenza Virus Characterization*:
CDC has characterized 305 influenza viruses [10 A(H1N1)pdm09, 239 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) : Seventy-eight (32.6%) of the 239 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 sixty-one (67.4%) of the 239 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.
Four influenza-associated pediatric deaths were reported to CDC during week 51. Three deaths were associated with an influenza A (H3) virus and occurred during weeks 49 and 50 (weeks ending December 6 and December 13, 2014, respectively). One death was associated with an influenza B virus and occurred during week 51 (week ending December 20, 2014).
A total of 15 influenza-associated deaths have been reported during the 2014-2015 season from nine states (Arizona , Colorado , Florida , Minnesota , North Carolina , Nevada , Ohio , 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 holiday gatherings upon us our focus now should be on practicing good flu hygiene.
- 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.