Orthomyxoviridae Influenza Virus

Properties Spherical Virion ( polymorphic) Spherical Virion ( polymorphic) 100 nm Size 100 nm Size Segmented –SS-RNA : 7-8 segments Segmented –SS-RNA : 7-8 segments Mostly segment: 1 protein and two segment 2 protein Mostly segment: 1 protein and two segment 2 protein H & N : Antigenic variation H & N : Antigenic variation Resistant to room temperature and spatially 4 º C Resistant to room temperature and spatially 4 º C

Neuraminidase helps the virus to release itself from the cells Hemagglutinin Hemagglutinin allows the virus to bind to host cells RNA Influenza Surface Proteins M 2 protein (only on type A)

Clinically Relevant Influenza Viruses Type APotentially severe illness Epidemics and pandemics Rapidly changing Type BUsually less severe illness Epidemics Genetically more stable

SubtypeHumanSwineHorseBird H1H2H3H4H5H6H7H8H9H10H11H12H13H14H15 Hemagglutinin Subtypes of Influenza A Virus Adapted from Levine AJ. Viruses. 1992;165, with permission.

SubtypeHumanSwineHorseBird N1N2N3N4N5N6N7N8N9 Neuraminidase Subtypes of Influenza A Virus Adapted from Levine AJ. Viruses. 1992;165, with permission.

Influenza A Virus Constantly Changes  Antigenic drift  Small changes in H or N proteins that occur from year to year  Antigenic shift  Acquisition of new H or N protein, possibly from an bird virus

Diseases : 1- Influenza:Signs and Symptoms  Abrupt onset of symptoms  Fever  Cough with little or no sputum  Headache  Muscle aches  Sore throat  light sensitivity, and eye pain

Pneumonia Pneumonia Elderly, pregnant, and ….. Viral (1:3), most viral & bacterial (S.areuse) (2:3) Reye Syndrome: encephalopathy in children (2-16 years), mortality 10-40%, Reye Syndrome: encephalopathy in children (2-16 years), mortality 10-40%, Influenza A & B, chicken pox, Salicylic acid compound

Immunity to influenza Permanat Permanat Type Related Type Related Antibody again H & N Antibody again H & N

Treatment Amantadine Amantadine Rimantadine RimantadinePrevention Vaccination ( 70%) Vaccination ( 70%)  Most effective in young, healthy people  Less effective in the elderly

Influenza Virus Vaccine