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6. Respiratory Viruses

6. Respiratory Viruses - Respiratory Tract Respiratory...

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Respiratory Viruses Respiratory Viruses “The Devil made me do it” The Devil made me do it” Respiratory Tract Upper respiratory tract •N o s e • Pharynx • Middle ear • Eustachian tubes • Sinuses Lower respiratory tract • Larynx • Trachea • Bronchi • Alveoli Defenses • Upper respiratory tract is defended by: – Nasal hair – Ciliated mucous membrane – Lymphoid tissue • Lower respiratory tract is defended by: – Ciliated mucous membrane – Alveolar macrophages –IgA Defenses • Cilated mucous membranes moisten air, trap large particles and move them to the upper respiratory tract where they are removed by coughing and sneezing. • Lymphoid tissue (tonsils and adenoids) play a role in the immune response. Local IgA antibodies are present in mucous, tears and saliva. General Characteristics of Respiratory Viruses • Seasonal – they peak in fall and winter months • Spread from person to person via respiratory secretions (on hands, fomites, by droplet) • Occur in outbreaks • Infants and the elderly most severely affected • Short incubation (hours to several days) • Common symptoms are runny nose, cough, + fever • Reinfection can occur throughout life (immunity is short-lived) • All RNA viruses with exception of adenovirus Viruses Which Cause Respiratory Infection Influenza Respiratory Syncytial Virus (RSV) Coronavirus
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Influenza • Orthomyxovirus family • Enveloped RNA virus • Two major serotypes, A and B infect humans • Most important feature – its ability to change its antigenic structure to evade host defenses – antigenic drift and antigenic shift Influenza Antigenic Components (surface proteins of the virus) S antigen – Soluble antigen from the protein core – all influenza As have one type of S antigen, influenza Bs have a different type H – Haemagglutinin glycoprotein spike which attaches virus to cells N – Neuraminidase glycoprotein spike which aids separation of newly formed viruses from cell Influenza • Influenza viruses are subtyped (named) based on their H and N components. • There are three types of Haemagglutinin (H1, H2, H3) and two types of Neuraminidase (N1, N2) in influenza viruses that commonly infect humans. • Other subtypes ie. H5N1 infect birds and animals. •E x am p l e s : Influenza viruses circulating in the 2003/2004 season – Influenza A/Panama/2007/99(H3N2) – Influenza A/Fujian/411/02(H3N2)
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6. Respiratory Viruses - Respiratory Tract Respiratory...

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