Influenza A H3N2v Health Alert Update
- This Health Alert Update replaces the Health Alert issued on August 9, 2012, at 9:00am PST.
- A recent increase in human cases with influenza A (H3N2v) infection has been reported in several states. Since July 2012, a total of 145 persons with confirmed H3N2v infection have been reported. The majority of cases have been in children with mild, self-limiting illness similar to seasonal influenza. No fatalities from H3N2v have been reported to date. National H3N2v case counts will be updated by the CDC every Friday at http://www.cdc.gov/flu/swineflu/influenza-variant-viruses-h3n2v.htm.
- No H3N2v cases have been detected in California to date.
- All cases reported nationwide since July 2012 had contact with swine prior to the onset of illness. There is no evidence of sustained human-to-human transmission of H3N2v in the community at this time. Exposure to swine at agricultural fairs appears to be a significant risk factor; individuals should take action to prevent the spread of viruses between people and also between people and pigs.
- The seasonal influenza vaccine is unlikely to provide protection against H3N2v; however, influenza vaccination is still recommended for protection against seasonal influenza viruses that are much more common causes of illness in humans than H3N2v.
- Treatment with oseltamivir or zanamivir is effective for H3N2v, and recommendations for antiviral use are the same as with seasonal influenza.
- This Health Alert Update provides information and recommendations regarding enhanced surveillance for H3N2v, including testing and reporting guidelines.
- During the summer months, encourage influenza testing in the following:
- All persons with influenza-like illness (ILI) — influenza-like illness = fever (>100°F or 37.8°C) and cough and/or sore throat, in the absence of a known cause — including severely ill/fatal cases and outpatients
- Acute respiratory outbreaks
- ILI in persons with recent swine exposures
- ILI in persons who can be epidemiologically linked to confirmed cases of novel or variant influenza.
- Collect respiratory specimens for RT-PCR testing at a Respiratory Laboratory Network (RLN) public health laboratory or the CDPH Viral and Rickettsial Disease Laboratory (CDPH-VRDL).
- Work with community partners, e.g., hospital clinicians and clinical laboratories, in local health jurisdictions to remind them of the importance of saving specimens of ILI cases during the summer months, so that further subtyping and characterization can be performed at a public health laboratory.
- Cases of influenza due to novel viruses are reportable in California and should be reported to the local health department. Local health departments should notify CDPH Communicable Disease Emergency Response Branch (CDER) immediately of any confirmed novel influenza cases or suspect cases that are very likely due to a novel virus. Report cases of novel influenza to CDPH-CDER [Email InfluenzaSurveillance@cdph.ca.gov or contact Cynthia Yen (Cynthia.Yen@cdph.ca.gov; (510) 231-6861) or Janice Louie (Janice.Louie@cdph.ca.gov; (510) 307-8567)].
- Continue mandatory reporting of laboratory-confirmed influenza in fatal cases age 0–64 years by using the severe influenza case history form (available at: http://www.cdph.ca.gov/HealthInfo/discond/Pages/Influenza(Flu).aspx)
- Continue voluntary reporting of laboratory-confirmed influenza cases age 0–64 years requiring intensive care by using the severe influenza case history form.
- During the summer months, CDPH strongly recommends the continued screening for influenza A and B on ILI specimens and subtyping using the full subtyping panel.
- Testing is available at CDPH-VRDL and at 28 RLN laboratories for presumptive identification of the H3N2v virus.
- Upper respiratory samples suitable for RT-PCR include: nasopharyngeal (NP swabs), nasal swabs, throat swabs, nasal aspirate, nasal washes, NP wash, and NP aspirate. For patients hospitalized with pneumonia, specimens from the lower respiratory tract should also be obtained. Lower respiratory tract samples suitable for RT-PCR include: bronchoalveolar lavage, bronchial wash, tracheal aspirate, and lung tissue.
- Place Dacron-tipped swabs (cotton or calcium alginate swabs are not acceptable for PCR testing) in a standard container with 2-3 ml of viral transport media (VTM).
- Specimens should be collected within the first 24-72 hours of onset of symptoms and no later than 5 days after onset of symptoms. The specimens should be kept refrigerated at 4°C and sent on cold packs if they can be received by the laboratory within 5 days of the date collected. If samples cannot be received by the laboratory within 5 days, they should be frozen at -70°C or below and shipped on dry ice.
- To detect swine origin influenza viruses and possible reassorted viruses, it is important that laboratories use a full subtyping panel (inf A, H3, pdm Inf A and pdm H1) when attempting subtyping.
- A presumptive identification of H3N2v will produce the following inconclusive result: Inf A (+), pdm InfA (+), H3 (+), pdm H1 (neg) and H1 (neg).
- Specimens with test results that are inconclusive or meet any of the following criteria should be submitted to CDPH-VRDL for further characterization:
- Unsubtypeable results with crossing threshold (Ct) value for Flu A ≤ 35.
- Inconclusive results for influenza 2009 AH1N1 with Inf A Ct ≤ 35.
- Specimens with results suggesting presence of more than one influenza virus (co-infections).
- Specimens with results suggesting presence of swine origin A/H3 virus; Inf A (+), H3 (+); pdm A (+) and pdm H1 (neg).
- RLN laboratories should refer to the Influenza Reference Examination form (available at: http://www.cdph.ca.gov/programs/vrdl/Pages/CurrentVRDLSpecimenSubmittalf...) for instructions on submission of specimens for further characterization at CDPH-VRDL.
- Questions regarding respiratory virus testing at CDPH-VRDL can be directed to Hugo Guevara [Email Hugo.Guevara@cdph.ca.gov or call 510-307-8565 or (510) 248-9855 (cell)].
- The CDC health advisory is available at http://www.bt.cdc.gov/HAN/han00325.asp
- For additional information on influenza A (H3N2v) in the United States, please refer to CDC’s website at: http://www.cdc.gov/flu/swineflu/influenza-variant-viruses-h3n2v.htm
- Information and materials about animals in public settings, including educational posters that can be displayed around animal exhibits, are available at: http://nasphv.org/documentsCompendiumAnimals.html
- The CDFA has a number of resources, including a swine influenza fact sheet, swine influenza Q&A for fair exhibitors, biosecurity recommendations for management of swine, and wash your hands signage, available at: http://www.cdfa.ca.gov/ahfss/Animal_Health/Swine_Health.html#Flu
- A CDPH H3N2v fact sheet as well as additional information about the California Influenza Surveillance Program is available at: http://cdph.ca.gov/HealthInfo/discond/Pages/Influenza(Flu).aspx