Avian influenza

Avian influenza

Avian influenza was not expected to cause disease in human beings.  However in 1997, an influenza epidemic broke out in Asia and North East Africa (WHO, 2011).  The avian subtype H5N1 had been incriminated for the several human diseases and deaths and was known to occur from infected poultry birds and farmyard animals as influenza A (CDC, 2009).  The WHO had worked with the aims of identification of new cases and made attempts to reduce animal health and public health risks (WHO, 2011).  The continuous effort by the World Health Organization had resulted in the WHO declaring that the world was not ready to contain an influenza epidemic in 2005.

The swine flu epidemic of 2009 made things look worse. Efforts since then had been consistently attempting to be ever-ready for an influenza epidemic through improving global surveillance and response capacity.  The H5N1 avian flu virus was highly pathogenic and had caused disease widely in wild birds and poultry (CDC, 2009).  It caused 408 human cases by February 2009.  Guidance for testing of suspected human cases infected with pathological avian flu with H5N1 influenza virus were provided.  Enhanced surveillance by local and national health care services was to continue.  Cases were to be notified to the local and national authorities immediately a presumptive diagnosis is made. Follow-up of cases was a necessity. In the US, information had to be transferred to the CDC (CDC, 2009).

Guidelines for diagnosis

Testing and reporting guidelines had been established by the CDC.  A person diagnosed presumptively with avian flu had to be hospitalized because it could end fatally.  Another requirement for hospitalization was that the temperature of the patient would be equal to or more than 38°C.  The patient could have any other respiratory illness like pneumonia or acute or severe respiratory illness (CDC, 2009).   Potential exposures occurring within seven previous days could be a reason for admission in the following conditions.  Direct contact with infected birds or animals or their feces was another reason for admission. Travel through a country with history of the virus caused by exposure to any animal or bird, intimate contact with a person with the influenza, close contact with a person who was a suspect and working in a laboratory with highly pathogenic live virus (CDC, 2009).  The infection was spread through droplet infection when in close contact.

Procedure for diagnosis

Clinicians needed to notify the local and higher authorities when a person was to be diagnosed using laboratory tests.  Specific guidelines were also followed for the clinicians who performed the specimen collection and testing.  Protective equipment for the clinicians was to be strictly used to prevent any contamination of the body parts with the suspected or confirmed person with H5N1 virus and when entering the room where aerosol generating procedures have been used where such a patient was lying in (CDC, 2009).  The respiratory protector (N-95) filtering face mask, goggles, face shield, latex gloves, gown and head covering were all included (CDC, 2009).  In the absence of a particulate respirator, other certified respirators like the NIOSH-certified N-, R-, or P-class respirators could be used.  The aerosol-generating procedures could be done only with the N-95 respirator or powered air purifying respirators (CDC, 2009).  Bronchoalveolar lavage was a high-risk aerosol generating procedure which required excellent protection.  If the clinician had a beard, a loose-fitting respirator could be used.  The virus could be detected from the bronchoalveolar lavage, oropharyngeal swabs, or endotracheal aspirate as these specimens usually had the virus.  The nasopharyngeal swab contained lesser virus so lower respiratory specimen should be taken (CDC, 2009).  However nasopharyngeal swabs sufficed for detection of influenza viruses A and B.  If most virus count needed to be isolated, multiple respiratory specimens from the same patient could be taken on other days too.   The specimen collection could be done by using swabs with a Dacron tip and aluminium shaft.  Immediate transfer was to be made into the sterile transport medium which was stored at the temperature of 4°C till the testing was done.   Rapid tests were never to be used for detection of influenza virus due to low sensitivity.  Negative results with these low sensitivity tests could not be believed to be negative for the presence of the virus H5N1 (CDC, 2009).    A positive result did not exclude influenza.  A virus or specify virus H5N1.  The tests had to be specific.

The laboratory testing staff had their own guidelines to rule out the possibility of being infected in the laboratory.  The diagnostic assay was the RT-PCR (H5-specific reverse-transcription polymerase chain reaction).  Virus inactivation and RNA stabilization was done by adding the nucleic acid extraction lysis buffer to the specimens (CDC, 2009).   The specimens could be shipped by maintaining the specimens at a temperature of 4°C or frozen at a temperature below -70°C and shipped on dry ice; intermediate thawing was not to be allowed.  Isolation of the virus or serological testing for H5N1-specific antibody was to be done only at the CDC.  The serology specimens could be collected at the first week of illness and then after 2 or 4 weeks (CDC, 2009).   A single specimen would be serologically tested if the patient died in between.  The result was considered positive when the rise of H5N1 specific antibody was obvious.  The current recommended test of microneutralization assay required live virus. Caution had to be taken to perform the testing of live virus in a USDA-approved Biosafety Level 3 enhanced containment facility (CDC, 2009).   The confirmatory test would be performed at the Influenza Division, National Center for Immunization and Respiratory Diseases, CDC.  This center was the WHO H5 Reference Laboratory (CDC, 2009).  Travel to any of the countries with a history of the H5N1 virus outbreaks was not restricted.

References:

Center for Disease Control and Prevention. Interim Guidance for Laboratory Testing of Persons with Suspected Infection with Highly Pathogenic Avian Influenza A (H5N1) Virus in the United States.  Available from http://www.cdc.gov/flu/avian/professional/guidance-labtesting.htm. 2009 CDC

WHO.  Avian Influenza 2011 http://www.who.int/mediacentre/factsheets/avian_influenza/en/index.html

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