Earlier this week, in It’s Beginning To Look A Lot Like . . . Flu Season, I wrote about the recent media reports on school absences (and some closures) due to influenza. You’ll also find some advice in that blog on the home treatment of flu, and when to seek medical care, from the CDC.
Although the CDC numbers, and maps, lag about a week behind current conditions - they clearly show that this year’s flu season is well underway across much of the middle of the nation.
With an overwhelmingly H3N2 dominant flu season so far – and a `mismatched’ strain reducing this year’s vaccine’s efficiency – the CDC has warned Early Data Suggests Potentially Severe Flu Season ahead. While the numbers don’t show us there yet – we are still below the `epidemic threshold’ for P&I Mortality – we are seeing steady week-to-week increases in flu activity.
Some excerpts from this week’s FluView report, then I’ll be back with a footnote.
All data are preliminary and may change as more reports are received.
During week 50 (December 7-13, 2014), influenza activity continued to increase in the United States.
- Viral Surveillance:Of 20,064 specimens tested and reported by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories during week 50, 5,200 (25.9%) 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:Four influenza-associated pediatric deaths were reported.
- Influenza-associated Hospitalizations: A cumulative rate for the season of 6.2 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 3.7%, above the national baseline of 2.0%. Nine of 10 regions reported ILI at or above region-specific baseline levels. Puerto Rico and 13 states experienced high ILI activity; six states experienced moderate ILI activity; New York City and five states experienced low ILI activity; 26 states experienced minimal ILI activity; and the District of Columbia had insufficient data.
- Geographic Spread of Influenza: The geographic spread of influenza in Guam and 29 states was reported as widespread; Puerto Rico and 14 states reported regional activity; the District of Columbia, the U.S. Virgin Islands and five states reported local activity; and two states reported sporadic activity.
Influenza Virus Characterization*:
CDC has characterized 248 influenza viruses [10 A (H1N1)pdm09, 209 A (H3N2), and 29 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) : Sixty-four (30.6%) of the 209 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 forty-five (69.4%) of the 209 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.
Four influenza-associated pediatric deaths were reported to CDC during week 50. Two deaths were associated with an influenza A (H3) virus and occurred during week 49 (week ending December 6, 2014). One death was associated with an influenza A virus for which no subtyping was performed and occurred during week 50 (week ending December 13, 2014), and one death was associated with an influenza B virus and occurred during week 49.
A total of 11 influenza-associated deaths have been reported during the 2014-2015 season from six states (Florida , Minnesota , North Carolina , Nevada , Ohio , and Texas ).
Additional data can be found at: http://gis.cdc.gov/GRASP/Fluview/PedFluDeath.html.
If you are looking for good news, none of the viruses this season have tested as being resistant to our two main antiviral drugs – Oseltamivir and Zanamivir.
This time last year, we were seeing nearly 2% of viruses showing signs of resistance.
While expected, and on a less positive note, the percentage of `drifted’ H3N2 viruses continues to climb, with apparently none of the (admittedly small number) of H3N2 viruses tested last week (n=12) matching the vaccine strain. In the week 49 FluView, of 84 viruses sequenced, less than 20% were a match.
As we often see Influenza B become more dominant towards the end of the flu season, this year’s flu shot may still offer you some welcome protection next spring, and the CDC suggests it might still provide some protection against this drifted strain.
For now, whether you got the shot or not, with holiday gatherings upon us our focus should be 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.