25. Influenza
pathogenesis
single stranded RNA influenza virus (orthomyxoviridae) inhaled and carried to lungs
viral hemagglutinin attaches to receptors on ciliated epithelial cells, viral envelope fuses with cell, viral RNA enters cell.
host cell synthesis is diverted to viral synthesis
formed visions bud from infected cell and released by viral neuraminidase, infect ciliated epithelium and mucus and alveolar cells
infected cells die, recovery of mucociliary escalator may take weeks
secondary bacterial infection of lungs occurs
virus exits through cough
symptoms
fever
muscle aches
lack of energy
headache
sore throat
nasal congestion
cough
incubation period- 1-2 days
transmission
inhaled droplets
antigenic drift
antigenic shift thwart immunity
prevention and treatment
amantidine and rimantadin prevent type A but not type B
vaccine 80-90% effective
epidemiology
at least 4 pandemics in 19th century
est 21 million deaths worldwide in 1918-1919 pandemic
3 types- A, B, C
A- moderate to sever, all age groups, humans and animals
B- mild epidemics, humans, primarily children
C- rarely in humans, not epidemic
can be used as treatment if given early
complications
pneumonia
Reye syndrome
myocarditis
death- 0.5-1/1000 cases
highest mortality rate in epidemic
over 65s
under 18mo
people with diabetes, heart diseases, kidney and resp ailments
antibodies produced after infection primarily IgG and must be sufficient in conc at site of invasion
appear 7 days after attack, max at 2 weeks
prevention
good ventilation of public buildings
avoid crowds in epidemics
cover faces when coughing