University:
Eastern Kentucky University
Course:
BIO 273 | Clinical Microbiology
Academic year:

2022
Views:

252

Pages:

3
Author:

Nesbyenvkk

Orthomyxovirus (-) Features: A few features of all negative sense viruses are: 1. They have their own RNA polymerase enzyme 2. All are single stranded (except Rheovirus) 3. All replicate in cytoplasm (except orthomyxovirus) Features of orthomyxoviruses are: 1. Enveloped 2. It has 8 virus segments 3. Most important virus in this family is influenza which has following strains: a. Influenza A (most important) i. Causes Pandemic ii. Causes Epidemic iii. Hence, it exhibits both antigenic drift and antigenic shift b. Influenza B i. Causes endemic outbreaks ii. Exhibits antigenic drift c. Influenza C Segmented viruses are BOAR: 1. Bunyavirus (3 segments) 2. Orthomyxovirus (8 segments) 3. Arenavirus (2 segments) 4. Reovirus (11 segments) Transmission: 1. Respiratory droplets 2. Flu season in US is typically from December to February (vaccine is usually administered in October) Pathogenesis: It can mutate by 2 ways: 1. Antigenic Drift a. It is a point mutation in viral genome b. It leads to changes in: i. Hemogluttinin (HA) ii. Neuraminidase (NA) c. Responsible for seasonal influenza (epidemics) 2. Antigenic Shift a. Reassortment b. Causes pandemics Details of HA and NA are given below: 1. Hemogluttinin a. Glycoprotein on surface of influenza viruses b. Binds to sialic acid which is found on membranes of cells of upper respiratory tract or on RBCs c. It causes RBCs to clump together in test tubes d. Influenza viruses which affect humans have following HA antigens (antigens determine cell tropism): i. H1 ii. H2 iii. H3 2. Neuraminidase a. Enzymes that cleave sialic acid to release newly formed virions from host cell 3. Process of viral infection a. Hemogluttinin binds to sialic acid b. Virus gets endocytosed into the cell c. Proper pH is required for viral uncoating i. pH is maintained by M2 protein Diseases: 1. Influenza a. Fever b. Myalgia c. Non-productive cough 2. Pneumonia a. Major complication of influenza 3. Guillain-Barre syndrome is associated with influenza Prevention: 1. Live, attenuated nasal spray 2. Killed form which is injectable a. Two forms are available i. Trivalent form contains 1. 2 influenza A strains 2. 1 influenza B strain ii. Quadravalent form contains 1. 2 influenza A strains 2. 2 influenza B strains Treatment: 1. Amantadine/Rimantadine a. Inhibits M2, hence inhibiting viral uncoating 2. Neuraminidase inhibitors a. Drugs: i. Oseltamivir ii. Anamivir b. NA inhibitors must be given early in course Aspirin is usually given in influenza without consulting a physician first. IT IS CONTRAINDICATED TO DO SO IN CASE OF CHILDREN. In children, aspirin can lead to Reyes Syndrome which is associated with: 1. Encephalitis 2. Fatty liver 3. Liver failure