Orthomyxoviridae, Paramyxoviridae

- Influenza virus

• (-) RNA, segmented (8); helical; enveloped
• *Replicate in nucleus

• A - Humans & other mammals; cause human disease
• B - Humans only; cause human disease
• C - Humans only

• - Surface spike on orthomyxovirus envelope, anchored by M protein
• - Binds to sialic receptors on cell membranes of upper resiratory tract, allowing adsorption to host cell memebrane
• - Cleaved into HA1 & HA2 --> infectivity

• - Major antigen
• - Subject to antibodies

• - Surface spike on orthomyxovirus envelope, anchored by M protein
• - Cleaves neuraminic acid in the mucin that covers and protects upper respiratory epithelial cells, allowing Hemagglutinin to adsorb to the cell membranes
• - Cleaves sialic acid receptor to allow release of virions from cell
• - Prevents mature virus from aggregating within infected cell

• - Major antigen
• - Subject to neuraminidase inhibitors

• - Point mutation changes in antigenic nature of HA or NA glycoproteins
• - Results in new strains that result in recurrent epidemics of influenza
• - Requires continual development of new vaccines

• - Most pronounced in Influenza A
• - Occurs in HA & NA
• - HA drift is more clinically significant

• - Major change in HA, NA, or both
• - Reults in new virus that results in pandemic of influenza
• - Genetic ressortment of avian and animal viruses

- Only occurs in Influenza A

• - Small-particle aerosol
• - Person-to-person
• - Eyes, Mouth
• - Esp. children
• - Esp. December-May

• - Fever, headache, chills, myalgia, malaise
• - Dry, explosive cough cough
• - Tracheobronchitis (upper respiratory)

• - Primary viral pneumonia (severe infection pt's)
• - Secondary bacterial pneumonia (immunocompromised pt's)

• - In children (3-5 mo.)
• - Characterisitic "seal-like barking" cough

- Airway swelling and narrowing secondary to upper respiratory infection (esp. parainfluenza virus, influenza virus)

• - Severe liver and brain disease
• - Children < 4yrs
• - Mortality 10-40%
• - Caused by aspirin administration to children with viral infection (esp. influenza B)

• *Never give aspirin to children for fever!
• - Give acetaminophene for antipyretic

• - Antiviral Drug against Influenza A
• - Targets M2 protein and prevents viral uncoating inside host cell

• - Antiviral Drug against Influenza A
• - Targets M2 protein and prevents viral uncoating inside host cell

• - Antiviral drug against Influenza
• - Prevents viral assembly and release from host cell

• - Inactivated
• - Prevents Influenza A & b
• - Contraindicated if severe egg allergy
• - Recommended for elderly, children, pregnant women, chronically ill (e.g. asthmatics), healthcare workers

• - Attenuated vaccination against influenza
• - Recommended for healthy 5-29 yrs

• - Strains resistant to Amantadine/Rimantadine
• - Sensitive to Neuraminidase inhibitors

• - Direct transmission from birds
• - 59% mortality rate

• - Two pig genes, one avian gene, one human gene
• - Not more lethal than seasonal flu
• - More pathogenic to young, healthy adults

• - Parainfluenza Virus
• - Respiratory Syncytial Virus (RSV)
• - Human Metapneumovirus (HMPV)
• - Measles
• - Mumps
• - Hendra Virus
• - Nipha Virus

• (-) RNA, non-segmented; Helical; Enveloped
• Replication in cytoplasm

• *HA and NA proteins are the in same glycoprotein spike
• *Fusion (F) protein causes fusion of infected host cells into syncytial cells

• - Adults: upper respiratory infection
• - Children: lower respiratory infection (+ croup) (+ pneumonia/bronchitis in infants)

• - Large droplets
• - Bodily secretions

None

#1 cause of pneumonia/bronchiolitis in infants/children

• - Adults: upper respiratory infection
• - Children: lower respiratory infection
• - Reinfection is the rule: usually upper respiratory

• - Large droplets
• - Person-to-person
• - Contact of surfaces

• Eye & Nose
• (not so much mouth)

• - Chronic pulmonary disease (e.g. asthma)
• - Increased risk of mortality for pt's with lung/cardiac/congenital anomalies

None

*Breastfeeding may confer IgA antibodies that can reduce severity of RSV infection

• - Rhinorrhea, cough, wheezing, rales
• - Bronchitis, Bronchiolotis, Pneumonia, Pharyngitis, Asthma exacerbation

• - Emerging Paramyxovirus
• - Natural Host: Fruit bats
• - Infected horses in Australia

• - Severe respiratory symptoms w/ systemic symptoms
• - High mortality

• - Emerging Paramyxovirus
• - Natural Host: Fruit bats
• - Infected pigs in Malaysia

• -Predominantly encephalitic symptoms (rather than respiratory)
• - High mortality