04/09/2013

This LOCS ADVISORY is a follow-up to a CDC HEALTH ADVISORY, Human Infections with Novel Influenza A (H7N9) Viruses, dated April 5, 2013. The CDC HEALTH ADVISORY describes the current situation and gives interim recommendations for public health and health care personnel.
 
In addition, the CDC HEALTH ADVISORY has links to other CDC documents, including one entitled Interim Guidance on Specimen Collection, Processing, and Testing for Patients with Suspect Influenza A(H3N2)v Virus Infection, which provides guidance on specimen collection and processing of samples,  http://www.cdc.gov/flu/swineflu/h3n2v-testing.htm. It is also included in this PDF.
 
Some significant excerpts from the HAN are provided below:
 
  • Patients with illness compatible with influenza who also meet either of the exposure criteria below should be candidates for RT-PCR testing for influenza. Decisions about diagnostic testing for influenza using RT-PCR should be made using available clinical and epidemiologic information, and additional persons in whom clinicians suspect influenza A (H7N9) virus infection may also be tested.

    *Patients with recent travel to countries where human cases of novel influenza A (H7N9) virus infection have recently been detected, especially if there was recent direct or close contact with animals (such as wild birds, poultry, or pigs) or where influenza A (H7N9) viruses are known to be circulating in animals. Currently, China is the only country that has recently reported novel influenza A (H7N9) human cases.

    *Patients who have had recent contact with confirmed human cases of infection with novel influenza A (H7N9) virus.
  • Clinicians should obtain a nasopharyngeal swab or aspirate from these patients, 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 or CDC. For additional guidance on diagnostic testing of patients under investigation for novel influenza A (H7N9) virus infection, please see Interim Guidance for Laboratory Testing of Persons with Suspected Infection with Highly Pathogenic Avian Influenza A (H5N1) Virus in the United States at http://www.cdc.gov/flu/avianflu/guidance-labtesting.htm.
 
  • If infection with influenza A (H7N9) virus is suspected based on current clinical and epidemiological screening criteria recommended by public health authorities, specimens should be collected with appropriate infection control precautions for novel virulent influenza viruses and sent to the state or local health department for testing. Viral culture should not be attempted in these cases.
 
  • All unsubtypeable influenza A virus specimens should be submitted to CDC immediately for additional diagnostic testing. At this time, confirmatory testing for avian influenza A (H7N9) will be conducted at CDC.
 
  • Commercially available rapid influenza diagnostic tests (RIDTs) may not detect avian or variant influenza A viruses in respiratory specimens. Therefore, a negative rapid influenza diagnostic test result does not exclude infection with influenza viruses. In addition, a positive test result for influenza A cannot confirm variant or avian influenza virus infection because these tests cannot distinguish between influenza A virus subtypes (they do not differentiate between human influenza A viruses and avian or variant viruses). Therefore, when RIDTs are positive for influenza A and there is concern for novel influenza A virus infection, respiratory specimens should be collected and sent for RT-PCR testing at a state public health laboratory. Clinical treatment decisions should not be made on the basis of a negative rapid influenza diagnostic test result since the test has only moderate sensitivity.
 

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