Skip directly to search Skip directly to A to Z list Skip directly to navigation Skip directly to page options Skip directly to site content

Interim Guidance on Influenza Antiviral Chemoprophylaxis of Persons Exposed to Birds with Avian Influenza A Viruses Associated with Severe Human Disease or with the Potential to Cause Severe Human Disease

This guidance pertains to avian influenza A (H7N9), Asian H5N1, and the newly detected avian influenza H5 viruses in the United States (H5N2, H5N8, and the new reassortant H5N1 virus).

Background

This document provides interim guidance for clinicians and public health professionals in the United States on follow-up and influenza antiviral chemoprophylaxis of persons exposed to birds infected with avian influenza A viruses associated either with severe human disease or thought to have the potential to cause severe human disease. Examples of viruses associated with severe human disease include Asian avian influenza A (H5N1) and A (H7N9) viruses. Examples of viruses with the potential to cause severe human disease include avian influenza A (H5N2) and (H5N8) viruses, and a new reassortant avian influenza A (H5N1) virus1, all of which were detected in wild and domestic birds in North America in December 2014 and January 2015. There is limited experience with these newly detected viruses to inform public health guidance. However, these viruses are thought to have the potential to infect people and cause severe illness. To date no human avian influenza infections have been documented in the U.S. CDC will update this guidance as additional information becomes available.

Exposure to Birds Infected with Avian Influenza

An exposed person is defined as a person with contact2 in the past 10 days3 to infected sick or dead birds, or infected flocks. Infected refers to infection with avian influenza A viruses associated with severe human disease or which have the potential to cause severe human disease.

 Top of Page

Monitoring of Exposed Persons

Exposed persons should monitor themselves for new illness for 10 days after the last known exposure. The presence of fever and respiratory symptoms (e.g., cough, sore throat, shortness of breath, difficulty breathing) should be assessed daily during this period.

Any exposed person who has a new fever or respiratory symptoms should be referred for prompt medical evaluation, antiviral treatment, and testing for avian influenza (A) virus infection.

Post-exposure Chemoprophylaxis of Exposed Persons

Chemoprophylaxis with influenza antiviral medications can be considered for all exposed persons. Decisions to initiate antiviral chemoprophylaxis should be based on clinical judgment, with consideration given to the type of exposure and to whether the exposed person is at high risk for complications from influenza.

If antiviral chemoprophylaxis is initiated, treatment dosing for the neuraminidase inhibitors oseltamivir or zanamivir (one dose twice daily) is recommended in these instances instead of the typical antiviral chemoprophylaxis regimen (once daily).4 For specific dosage recommendations for treatment by age group, please see Influenza Antiviral Medications: Summary for Clinicians. Physicians should consult the manufacturer’s package insert for dosing, limitations of populations studied, contraindications, and adverse effects. If exposure was time-limited and not ongoing, five days of medication (one dose twice daily), from the last known exposure is recommended.

Chemoprophylaxis is not routinely recommended for personnel involved in culling non-infected or likely non-infected bird populations as a control measure or personnel involved in handling sick birds or decontaminating affected environments (including animal disposal) who used proper personal protective equipment.

See CDC guidance for follow-up and antiviral chemoprophylaxis of contacts of cases of human infection with avian influenza A viruses associated with severe human disease.

Footnotes

1 The H5N1 virus isolated from a US wild bird is a new mixed-origin virus (a “reassortant”) that is genetically different from the avian H5N1 viruses that have caused human infections with high mortality in several other countries (notably in Asia and Africa). No human infections with this new reassortant H5N1 virus have been reported.

2 This direct exposure may include: contact with birds (e.g., handling, slaughtering, defeathering, butchering, preparation for consumption); direct contact with surfaces contaminated with feces or bird parts (carcasses, internal organs, etc.); or prolonged exposure to birds in a confined space.

3 The potential incubation period is unknown for avian influenza A viruses which are not yet known to cause human disease. Available data suggest that the estimated incubation period for human infection with H5N1 and H7N9 viruses is generally 3 to 7 days, but has been reported to be as long as 10 days.

4 This recommendation for twice daily antiviral chemoprophylaxis dosing frequency is based on limited data that support higher chemoprophylaxis dosing in animals for avian A(H5N1) virus (Boltz DA, et al JID 2008;197:1315) and the desire to reduce the potential for development of resistance while receiving once daily dosing ( BazM, et al NEJM 2009;361:2296; Cane A et al PIDJ 2010;29:384; MMWR 2009;58:969).

 Top of Page

Avian influenza A viruses with the potential to cause severe human disease currently include the following viruses detected in wild and domestic birds in the United States beginning in December 2014:

  • Highly pathogenic avian influenza A (H5N2) virus
  • Highly pathogenic avian influenza A (H5N8) virus
  • Highly pathogenic avian influenza A (H5N1) virus
  • Avian influenza A (H7N8) virus

Avian influenza A viruses associated with severe human disease currently include the following:

Guidance Type

Viruses

Summary for Clinicians

Summary of guidance for all viruses that have the potential to cause severe disease

Testing and Reporting

Guidance for all viruses that have the potential to cause severe disease

Case Definitions

HPAI H5 in the United States

Infection Control

See guidance for viruses associated with severe disease

Treatment

See guidance for viruses associated with severe disease

Chemoprophylaxis of Persons Exposed to Birds

Guidance for all viruses that have the potential to cause severe disease

Chemoprophylaxis of Followup of Close Contacts

See guidance for viruses associated with severe disease

Avian influenza A viruses with the potential to cause severe human disease currently include the following viruses detected in wild and domestic birds in the United States beginning in December 2014:

  • Highly pathogenic avian influenza A (H5N2) virus
  • Highly pathogenic avian influenza A (H5N8) virus
  • Highly pathogenic avian influenza A (H5N1) virus
  • Avian influenza A (H7N8) virus

Guidance Type

Viruses

Summary for Clinicians

Summary of guidance for all viruses that have the potential to cause severe disease

Testing and Reporting

Guidance for all viruses that have the potential to cause severe disease

Case Definitions

HPAI H5 in the United States

Infection Control

See guidance for viruses associated with severe disease

Treatment

See guidance for viruses associated with severe disease

Chemoprophylaxis of Persons Exposed to Birds

Guidance for all viruses that have the potential to cause severe disease

Chemoprophylaxis of Followup of Close Contacts

See guidance for viruses associated with severe disease

Avian influenza A viruses associated with severe human disease currently include the following:

Guidance Type

Viruses

Summary for Clinicians

Not available

Testing and Reporting

Guidance for all viruses that are associated with severe disease

Case Definitions

H7N9

Asian-lineage H5N1

Infection Control

Guidance for all viruses that are associated with severe disease

Treatment

Guidance for all viruses that are associated with severe disease

Chemoprophylaxis of Persons Exposed to Birds

Guidance for all viruses that are associated with severe disease

Chemoprophylaxis and Followup of Close Contacts

Guidance for all viruses that are associated with severe disease

Top