Saturday, January 31, 2015

CDC Interim Guidance On Antiviral Chemoprophylaxis For Persons With Exposure To Avian Flu


Photo Credit – FAO


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Last night the CDC released a pair of interim guidance documents for clinicians and public health officials on how to deal with patients suspected of being exposed to novel (primarily avian) influenza. I blogged about the first guidance document earlier today in CDC Interim Guidance For Testing For Novel Flu.

Although we haven’t had to deal with HPAI much in North America, the standard procedure it to treat – prophylactically with antivirals – anyone with known exposure to infected birds. 


Often in Asia or the Middle East, this has included cullers who have been charged with destroying an infected flock of poultry, or family members of someone diagnosed with H5N1 or H7N9.  With the recent arrival of HPAI H5 viruses in migratory and wild birds to North America, it is possible that some North American poultry workers (or hunters) may be exposed to infected birds. 


While the HPAI H5 viruses currently circulating in North America have not been directly associated with human infection, viruses evolve over time, and the CDC is wisely considering them a potential human health hazard.  The CDC has therefore released the following interim guidance.


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 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.

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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.

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.


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).

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