Avian Influenza H5N1 Prepared by: Samia ALhabardi

Introduction: What is avian influenza (bird flu)? Bird flu is an infection caused by avian (bird) influenza (flu) viruses. These flu viruses occur naturally among birds. Wild birds worldwide carry the viruses in their intestines, but usually do not get sick from them. However, bird flu is very contagious among birds and can make some domesticated birds, including chickens, ducks, and turkeys, very sick and kill them

Types, Subtypes, and Strains  There are three types of influenza viruses: A, B, and C. Influenza Type A Influenza type A viruses can infect people, birds, pigs, horses,, and other animals, but wild birds are the natural hosts for these viruses. Influenza type A viruses are divided into subtypes based on two proteins on the surface of the virus. These proteins are called hemagglutinin (HA) and neuraminidase (NA). There are 15 different HA subtypes and 9 different NA subtypes. Many different combinations of HA and NA proteins are possible. Only some influenza A subtypes (i.e., H1N1, H1N2, and H3N2) are currently in general circulation among people. Other subtypes are found most commonly in other animal species..

Influenza Type B Influenza B viruses are normally found only in humans. Unlike influenza A viruses, these viruses are not classified according to subtype. Although influenza type B viruses can cause human epidemics, they have not caused pandemics Influenza Type C Influenza type C viruses cause mild illness in humans and do not cause epidemics or pandemics. These viruses are not classified according to subtype. Strains Influenza B viruses and subtypes of influenza A virus are further characterized into strains. There are many different strains of influenza B viruses and of influenza A subtypes. New strains of influenza viruses appear and replace older strains. This process occurs through a type of change is called “drift” (see How Influenza Viruses Can Change: Shift and Drift). When a new strain of human influenza virus emerges, antibody protection that may have developed after infection or vaccination with an older strain may not provide protection against the new strain. Thus, the influenza vaccine is updated on a yearly basis to keep up with the changes in influenza virusesHow Influenza Viruses Can Change: Shift and Drift

Symptoms of Avian Influenza in Humans The reported symptoms of avian influenza in humans have ranged from typical influenza- like symptoms (e.g., fever, cough, sore throat, and muscle aches) to eye infections (conjunctivitis), pneumonia, acute respiratory distress, viral pneumonia, and other severe and life-threatening complications

Global spread 2004/2005

H5N1 Structure

MICROSCOPIC EXAMENATION Influenza A virus, the virus that causes Avian flu. Transmission electron micrograph of negatively stained virus particles in late passage,

Transmission of Influenza A Viruses Between Animals and People Avian influenza A viruses may be transmitted from animals to humans in two main ways: Directly from birds or from avian virus-contaminated environments to people. Through an intermediate host, such as a pig.

Laboratory Testing Procedures Highly pathogenic avian influenza A (H5N1) is classified as a select agent and must be worked with under Biosafety Level (BSL) 3+ laboratory conditions CDC does not recommend that virus isolation studies on respiratory specimens from patients. Therefore, respiratory virus cultures should not be performed in most clinical laboratories and such cultures should not be ordered for patients suspected of having H5N1 infection. Specimens from persons should be sent to CDC if The specimen tests positive for influenza A by PCR or by antigen detection testing, OR PCR assays for influenza are not available at the state public health laboratory.

Atypical Avian Influenza (H5N1 A) Chest radiograph on hospital day 5 at referring hospital shows patchy infiltration at bilateral lower lung fields. B) Chest radiograph upon admission to our hospital (24 hours later) shows rapidly progressive pneumonia in both lung fields, compatible with adult respiratory distress syndrome

Antiviral Agents for Influenza Four different influenza antiviral drugs (amantadine, rimantadine, oseltamivir, and zanamivir) are approved by the U.S. Food and Drug Administration (FDA) for the treatment of influenza; three are approved for prophylaxis. All four have activity against influenza A viruses. However, sometimes influenza strains can become resistant to these drugs, and therefore the drugs may not always be effective. For example, analyses of some of the 2004 H5N1 viruses isolated from poultry and humans in Asia have shown that the viruses are resistant to two of the medications (amantadine and rimantadine )..

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