Part one (written by second year Nick Mancuso) will cover the important basics about the flu epidemic this season. Great summary!
The 2012/13 vaccine contains the typical triad against an H1N1, H3N2, and an influenza B variant.
- A/California/7/2009 (H1N1)-like virus
- A/Victoria/361/2011 (H3N2)-like virus
- B/Wisconsin/1/2010-like virus.
Symptoms overlap with many URI’s, however the classics:
Abrupt onset, Chills, Varying fever temps, Myalgias, Frontal/retro-orbital headache, Sore throat, Nausea/Vomiting
can be difficult because samples are sent to labs and take time to get results. A nasopharyngeal culture is taken. Most diagnosis is done at the bedside based on clinical criteria. Rapid tests are not accurate and results vary. (Check continue reading for more info about diagnostic tests!)
Read part 2!
For some cool data and graphs from the CDC continue reading…
Anyone who has had the news on knows, this year’s flu season is expected to be, and already is, a bad one. Walk into your local Emergency Department and everyone is wearing the iconic mask, sitting in the waiting room because of overcrowding and other illnesses peaking. Here’s a brief summary of this year’s seasonal flu so far:
The vaccine is recommended for everyone over 6 months old, especially children, pregnant women, the elderly, and healthcare workers. Administration is IM, infants and younger children should be vaccinated in the anterolateral thigh, adults and older children, the deltoid is preferred. 6 through 35 months receive 0.25 mL per dose; persons aged ≥36 months receive 0.5 mL per dose. FluMist intranasal is given via a 0.2 mL prefilled intranasal sprayer to those over 2 years old. As of 12/14/12 127 million doses had been distributed. http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6132a3.htm#fig1
Characterized cases so far by the CDC include:
-100% of 17 H1N1 viruses tested were characterized as A/California/7/2009-like
-(99.3%) of the 281 H3N2 influenza viruses tested have been characterized as A/Victoria/361/2011-like
-(68.7%) of the 115 influenza B viruses tested so far this season have been characterized as B/Wisconsin/1/2010-like
-(31.3%) of 115 influenza B viruses tested have been from the B/Victoria lineage of viruses
- Since the start of the season, influenza A (H3N2) viruses have predominated nationally, followed by influenza B viruses, while 2009 H1N1 viruses have been identified rarely. The predominant circulating virus has varied by state and by region. (http://www.cdc.gov/flu/weekly/)
Diagnostic tests for the Flu
From the CDC:
- Rapid Influenza Diagnostic Tests (RIDTs) can be useful to identify influenza virus infection as a cause of respiratory outbreaks in any setting. RIDTs produce very quick results, but the results may not be accurate. Sensitivities of RIDTs are generally 40-70%, but a range of 10-80% has been reported compared to viral culture or reverse transcription polymerase chain reaction (RT-PCR). Specificities of RIDTs are approximately 90-95% (range 85-100%). Thus, false negative results occur more commonly than false positive results. In particular, false negative test results are common during influenza season. Clinicians should realize that a negative RIDT result does NOT exclude a diagnosis of influenza in a patient with suspected influenza.
- Other testing (immunofluorescence, RT-PCR, viral culture) is more accurate, but can take longer. When influenza is suspected and antiviral treatment is indicated, antiviral treatment should begin as soon as possible and should not wait for the results of testing.
To Minimize False RIDT Results
- Collect specimens as early in the illness as possible (ideally less than 4 days from illness onset).
- Follow-up negative results with confirmatory tests (RT-PCR or viral culture) if a laboratory-confirmed influenza diagnosis is desired.
“FDA approves vaccines for the 2012-2013 influenza season”. Press Release. FDA. http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm315365.htm
Oseltamivir phosphate package insert http://www.gene.com/download/pdf/tamiflu_prescribing.pdf
“Seasonal Influenza Vaccination Resources for Health Professionals.” web http://www.cdc.gov/flu/professionals/vaccination
Compiled by: Nick Mancuso
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