Health

Advisory

INCREASE IN INFLUENZA A H3N2v VIRUS INFECTIONS IN U.S.

Delaware is not among three states reporting cases of Influenza A H3N2v virus and has had not reported any case of seasonal influenza

since June 12th, 2012. Typically, the flu season occurs in the fall and winter but the peak of flu season has occurred anywhere from late November through March.

Nationally, multiple infections with variant* influenza A (H3N2v) viruses have been identified in 3 states in recent weeks. From July 12

through August 3, 2012, 16 cases of H3N2v were reported and confirmed by Centers for Disease Control (CDC). This virus was first detected

in humans in July 2011. It has also been isolated in U.S. swine in many U.S. states. Since July 12, 2011, there have been 29 cases of

H3N2v virus infection. The H3N2v viruses have been reported in the following states: Hawaii (1), Indiana (7), Iowa (3), Ohio (10), Maine

(2), Pennsylvania (3), Utah (1), and West Virginia (2).

All 29 cases were infected with H3N2v viruses that contain the matrix (M) gene from the influenza A (H1N1)pdm09 virus. This M gene may

make transmission easier to and among humans, compared to other variant influenza viruses. All cases have been laboratory-confirmed at

CDC. Each of the 16 cases identified since July 12, 2012, reported contact with swine prior to illness onset; in 15 cases, contact

occurred while attending or exhibiting swine at an agricultural fair. While the viruses identified in these cases are genetically nearly

identical, separate swine exposure events in each state were associated with human infections. There is no indication that the cases in

different states are related epidemiologically.

Clinical characteristics of the 16 H3N2v recent cases have been generally consistent with signs and symptoms of seasonal influenza, and

have included fever, cough, pharyngitis, myalgia, and headache. No hospitalizations or deaths have occurred among the 16 confirmed cases

since July 2012. Public health and agriculture officials are investigating the extent of disease among humans and swine, and additional

cases are likely to be identified as the investigation continues.

Interim Recommendations for Health Care Providers

• Clinicians who suspect influenza in persons with recent exposure to swine should obtain a nasopharyngeal swab or aspirate from thepatient, place the swab or aspirate in viral transport medium, and contact the Public Health Laboratory at 302-223-1520 to arrange

  transport and request a timely diagnosis.

• Reverse-transcription polymerase chain reaction (RT-PCR) testing for influenza should be considered for patients with influenza-likeillness prior to the start of the traditional influenza season in October.
• RT-PCR testing for influenza should be considered throughout the year for patients with influenza-like illness reporting recent swineexposure and for those who can be epidemiologically linked to confirmed cases of variant influenza.
• Commercially available rapid influenza diagnostic tests (RIDTs) may not detect H3N2v virus in respiratory specimens. Therefore, anegative rapid influenza diagnostic test result does not exclude infection with H3N2v or any influenza virus. In addition, a positive

  test result for influenza A cannot confirm H3N2v virus infection because these tests cannot distinguish between influenza A virus

  subtypes (they do not differentiate between human influenza A viruses and H3N2v virus). Therefore, respiratory specimens should be

  collected and sent for RT-PCR testing to the Public Health Laboratory.

• Clinicians should consider antiviral treatment with oral oseltamivir or inhaled zanamivir in patients with suspected or confirmedH3N2v virus infection. Antiviral treatment is most effective when started as soon as possible after influenza illness onset.

Testing

DPH strongly encourages providers (for example, school wellness centers, long term care facilities, physicians, etc.) to submit influenza

specimens to the DPH Laboratory for culture molecular (PCR) confirmation and subtyping (throat/NP/nasal wash) to assist with the

detection of influenza. To submit a specimen for culture influenza testing, contact the Public Health Laboratory (302-223-1520) to

request influenza virus isolation kits and obtain information about specimen transport to the laboratory. Culture Molecular detection and

subtype testing by the Public Health Laboratory is done free of charge and results are sent back to the requesting physician or hospital

as soon as test results are available.

Novel influenza A virus infection has been a nationally notifiable condition in the United States since 2007. Since that time, human

infection with animal-origin influenza viruses has been rare, with ≤6 cases reported each year, until 2011 when 14 cases were

identified. While most of the cases are thought to have been infected as a result of close contact with swine, limited human-to-human

transmission of this virus was identified in some cases in 2011. Therefore, enhanced influenza surveillance is indicated, especially in

regions and states with confirmed H3N2v cases.

For more information

• DPH Epidemiology: 1-888-295-5156
• Public Health Laboratory: (302) 223-1520
• “Interim Guidance on Case Definitions to be Used for Investigations of Influenza A (H3N2) Variant Virus Cases” for stateand local health departments is available at http://www.cdc.gov/flu/swineflu/case-definitions.htm.
• “Prevention Strategies for Seasonal and Influenza A(H3N2)v in Health Care Settings” is available at http://www.cdc.gov/flu/swineflu/prevention-strategies.htm.
• “Interim Guidance on Specimen Collection, Processing and Testing for Patients with Suspected Influenza A (H3N2) Variant VirusInfection” for public health professionals is available at http://www.cdc.gov/flu/swineflu/h3n2v-testing.htm, and
• “Interim Guidance for Influenza Surveillance: Additional Specimen Collection for Detection of Influenza A (H3N2) VariantInfections” for state and local health departments is available at http://www.cdc.gov/flu/swineflu/h3n2v-surveillance.htm.
• Compendium of Measures to Prevent Disease Associated with Animals in Public Settings, 2011 is available at http://nasphv.org/documentsCompendiumAnimals.html

*Variant:Influenza viruses that circulate in swine are called swine influenza viruses when isolated from swine, but are called variant

viruses when isolated from humans

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