Photo Credit CDC
# 6453
Today’s MMWR from the CDC carries a brief report on the outbreak, in humans and swine, of the H3N2v flu virus that I blogged on twice yesterday (see Reports Of H3N2v In Indiana and ISDH Statement On H3N2v).
Among other things, this report confirms that this virus is indeed similar to the H3N3v viruses we’ve seen since August of 2011; a reassortment of the swine H3N2 virus with the Matrix (M) gene segment from the 2009 H1N1 virus.
All four confirmed cases have recovered, and none required hospitalization. This is obviously a very early report from the field, and I expect we’ll see more detailed information in the future.
Notes from the Field: Outbreak of Influenza A (H3N2) Virus Among Persons and Swine at a County Fair — Indiana, July 2012
Weekly
July 27, 2012 / 61(29);561-561
During July 12–16, 2012, the Indiana State Department of Health and the Indiana Board of Animal Health identified respiratory illness among swine and persons at a county fair held July 8–14. On July 16, specimens were collected from four persons with respiratory illness; two had become ill on July 12 and sought care at an emergency department, and two were identified as part of the subsequent public health investigation. All four persons were swine exhibitors or family members of swine exhibitors and had close contact with swine. On July 18, reverse transcription–polymerase chain reaction testing at the Indiana State Department of Health laboratory identified suspected influenza A (H3N2) variant (H3N2v) virus* in all four specimens. On July 21, partial genome sequencing at CDC confirmed H3N2v virus with the influenza A (H1N1)pdm09 virus M gene; the viruses detected in the four specimens are similar to 12 viruses detected in 2011 and one detected earlier this year (1). None of the four persons were hospitalized, and all have fully recovered.
Additionally, all respiratory specimens collected from a sample of 12 swine at the fair were positive for influenza A (H3N2) virus. The specimens were forwarded to the National Veterinary Services Laboratories of the U.S. Department of Agriculture for additional testing. Preliminary genetic analysis has shown a very high level of similarity between the gene sequences of H3N2v viruses from humans and the H3N2 viruses from swine.
Although human-to-human transmission of H3N2v has been limited in previous outbreaks (1), these viruses could change to transmit efficiently among humans. Clinicians who suspect influenza in persons with recent exposure to swine should obtain a nasopharyngeal swab or aspirate from the patient, place the swab or aspirate in viral transport medium, and contact their state or local health department to arrange transport and request a timely diagnosis at a state public health laboratory (1). Clinicians should consider antiviral treatment with oral oseltamivir or inhaled zanamivir in suspected cases (2). Persons who raise swine or come into close contact with swine at fairs or other venues should be aware of the potential risk for influenza transmission between swine and humans. To reduce this risk, preventive measures such as practicing frequent hand hygiene and respiratory etiquette are recommended. Persons also should avoid close contact with animals that look or act ill, when possible, and if experiencing influenza-like illness themselves, should avoid contact with swine. Additional guidelines on prevention of influenza transmission between humans and swine are available at http://www.cdc.gov/flu/swineflu/industry_guidance.htm.
Including the cases in this report, 17 infections with H3N2v virus with the influenza A (H1N1)pdm09 virus M gene have been reported since August 2011. Novel influenza A virus infection in humans is a nationally notifiable disease (3) and a reportable disease under International Health Regulations (4). State public health laboratories should contact CDC and send all suspected novel influenza A specimens for confirmatory testing. Additional information about H3N2v is available at http://www.cdc.gov/flu/swineflu/influenza-variant-viruses-h3n2v.htm.
