Avian Influenza

Avian influenza due to H5N1 has occurred almost exclusively in patients in Asia with close contact to chickens. It is not entirely clear whether person to person transmission has occurred. However, this patient could have developed any of a number of processes in Asia or on the airplane. It is helpful to know when the symptoms started. Since influenza has an incubation period of 1 to 2 days, this illness could be influenza acquired in Asia.
Influenza requires droplet precautions, and not airborne. Respiratory isolation (ÔÇťairborne precautions) is appropriate until the etiology of a respiratory illness is determined. There are actually very few infections that are spread by aerosol: varicella, disseminated zoster, measles, tuberculosis are the most common examples in the US. Monkey pox, small pox, SARS, and Viral hermorrhagic fevers require airborne precautions as well. Most other respiratory infections are spread by droplet.
In fact, contact isolation IS appropriate for most diseases that require airborne (eg, all of those listed above except measles and TB).

However, influenza only requires droplet. In this patient, however, at this point the etiology is not known.

Airborne precautions includes a private room with negative airflow (at least 6 air exchanges per hour, and all personnel entering the room should have a personal respirator that filters 1u particles (ie, an N95 mask or a PAPR).

Droplet precautions require a private room but no special air handling, and surgical masks rather than N95.

For empiric or specific therapy directed against seasonal or pandemic influenza, there is no parenteral therapy. Rimantidine resistance is widespread. There is no reason to use this drug with current strains.
Oseltamivir should be used: while there is no convincing data that this changes the course of pneumonia, it is plausible to use.


References

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  • de Jong MD, Bach VC, Phan TQ, et al. Fatal avian influenza A (H5N1) in a child presenting with diarrhea followed by coma. N Engl J Med. 2005;352:686-691.
  • Gu J, Xie Z, Gao Z, et al. H5N1 infection of the respiratory tract and beyond: a molecular pathology study. Lancet. 2007;370:1137-1145.
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  • Smith NM, Bresee JS, Shay DK, et al; Advisory Committee on Immunization Practices (ACIP). Prevention and control of influenza: recommendations of the ACIP. MMWR Recomm Rep. 2006;55:1-42.
  • Sandrock C, Kelly T. Clinical review: Update of avian influenza A infections in humans. Critical Care 2007; 11:209 (22 March 2007)