Wednesday, February 22, 2012

Weekly Influenza Update

Report on  the week ending February 17, 2012

Wisconsin: 

Wisconsin continues to have remarkably low influenza activity. 

89% of viruses have been A(H3N2) and 11% (H1N1).  The prevalence of influenza-like illness [fever of 100°F or higher and either cough or sore throat] in Wisconsin's primary care patients is estimated to be 1.2% and is stable.

14.7% of last week's primary care patients had all-cause respiratory infections.

The prevalence of acute diarrheal illness (ADI) in Wisconsin's primary care patients is at 2.0%.

Primary Care Snapshot:

The most common identified cause of Acute Respiratory Infection (ARI) in Wisconsin surveillance clinics is a mixture of Human Metapneumovirus, Parainfluenza, RSV, Coronavirus and Influenza A.  Over the past 4 weeks the typical ARI case presenting for primary care has been 35.5 years old and 73% of patients have been female.  58% of patients identified a sick contact 1-3 days before illness onset and typically presented to the clinic 3.7 days after illness onset.  42% of illnesses are characterized as mild, with 56% having moderate symptoms and 2% having severe symptoms.

Typical symptoms include:

  • cough - 88%
  • sore throat - 71%
  • nasal congestion - 71%
  • nasal discharge - 67%
  • fever - 48%
  • headache - 42%

Clinical Notes:

Prophylaxis

There appears to be an excellent match between the current influenza vaccine and circulating strains.

  • Influenza vaccine is recommended for everyone 6 months and older, including pregnant women.
  • Pneumococcal vaccine (PPSV-23) for adult smokers, asthmatics and a number of other chronic conditions.

Diagnosis

  • Influenza infections are at low levels at this time.
  • PPV of rapid antigen tests at this time is moderate.
  • NPV of rapid antigen tests at this time is high.

Treatment

  • Antivirals need to be started with 48 hours of symptom onset to be effective against influenza.
  • Antivirals started after 48 hours may be effective for hospitalized patients with confirmed influenza.

Resistance Patterns

  • All tested recent influenza A and B isolates have been sensitive to oseltamivir and zanamivir.
  • High levels of adamantine resistance exist in influenza A isolates from around the world.

Other

  • Rhinoviruses predominate Wisconsin isolates from patients with respiratory infection.
  • RSV activity is increasing in Wisconsin.
  • Human metapneumovirus, adenoviruses, coronaviruses and parainfluenza viruses are co-circulating at low levels.

Pertussis

Across the U.S.:

378 (10.5%) respiratory specimens during week 5 (January 29 - February 4, 2012) were positive for influenza.

For the 2011-2012 influenza season:

  • 88.3% of subtyped isolates have been type A
  • 14.0% of all sub-typed A viruses have been 2009 H1N1
  • 86% of A viruses have been H3N2
  • 11.7% of isolates have been type B
  • 7.3% of deaths during week 5 (January 29-February 4, 2012) were due to pneumonia or influenza [slightly above the seasonally-adjusted epidemic threshold of 7.8%]
  • two pediatric deaths have been reported this season.

The Weekly Influenza Update is adapted by WAFP from an email by Jon Tempte, Secretary of HHS to the US Advisory Committee on Immunization Practice

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