Cause: Influenza virus (Orthomyxovirus) - strains designated A, B,
C and by HA and NA antigens
Transmission: airborne
Symptoms: fever, malaise, myalgia, pharyngitis, cough, otitis
media, GI upset
Complications: pneumonia, carditis, encephalitis
Pathogenesis: Primary infection of mucoepithelium causes cytopathic
effect, local inflammation and loss of epithelial cells, esp.
ciliated/mucus-producing cells. Systemic symptoms are due to interferons.
Treatment: Supportive; amantadine (uncoating inhibitor),
oseltamivir (NA inhibitor)
Immunity: intermediate
Vaccine: annual vaccine needed - effective only against some
strains