November 9, 2017 Volume 1

Orange County has reported its first influenza-associated death of the season in a person less than 65 years of age. The decedent was a previously healthy toddler who was not vaccinated this season. All persons 6 months of age and older are recommended to get influenza vaccine annually. Influenza vaccine is readily available at numerous locations throughout the county; see www.ochealthinfo.com/phs/about/family/flu for more information.

Current Situation:  Since week 41 (ending 10/14/2017), influenza activity in Orange County has been elevated earlier this season compared to the past four years. Influenza A/H3 has been the most frequently identified influenza virus by Orange County Public Health Laboratory thus far in the season. Very few detections of influenza A/(H1N1)pdm2009 and influenza B have been reported.

Influenza Testing: Rapid influenza diagnostic tests (RIDTs) utilizing antigen detection are generally only 50-70% sensitive and should not be relied on for diagnosis of influenza or for clinical management and treatment decisions. Reverse transcription-polymerase chain reaction (RT-PCR) and other molecular assays have high sensitivity and specificity and are the preferred testing modality for hospitalized patients and other patients for whom influenza testing results would influence clinical management. Respiratory specimens should be collected as close to illness onset as possible (ideally within the first 3-4 days) to maximize virus detection. The CDC has developed an algorithm to assist providers with deciding when to consider influenza testing ( www.cdc.gov/flu/professionals/diagnosis/consider-influenza-testing.htm ) and how to interpret influenza test results ( www.cdc.gov/flu/professionals/diagnosis/algorithm-results-circulating.htm ).  Empiric therapy for suspected influenza should not be delayed while awaiting testing results in hospitalized patients or those at high risk for complications of influenza.

Influenza Treatment:   Antiviral treatment with neuraminidase inhibitors (e.g., oseltamivir, zanamivir, or peramivir) should be started as soon as possible in the following patients: Hospitalized patients with suspected or confirmed influenza Patients with progressive disease Patients who are at high risk for influenza complications.*  Dosing information is available at www.cdc.gov/flu/professionals/antivirals/summary-clinicians.htm . Although antiviral treatment is of the most benefit when started within 48 hours of symptom onset, patients hospitalized later in illness may still benefit. History of current season vaccination does not exclude an influenza diagnosis.

Influenza Vaccination: See the latest Advisory Committee on Immunization Practices (ACIP) recommendations in the 8/25/17 MMWR Recommendations and Reports available at www.cdc.gov/mmwr . *See www.cdc.gov/flu/professionals/antivirals/antiviral-use-influenza.htm  for list of high risk conditions.

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