Priscilla Johanesen; Week 12 MED1011; Microbiology
Epidemiological factors and sociopolitical factors determine whether a microbe is of medical importance. Medical importance is dictated by treatable/vaccinatable diseases vs non treatable. Epidemic is level of disease above normal for community. Outbreak is sudden or unexpected occurrence of disease within a limited segment of populaiton. Endemic is a disease consistently present in a population.
Influenza is orthomyxovirus, 8 segments of RNA enveloped with antigens on protein coat, glycoproteins. H mediates binding of virus to the target cell and entry of viral genome. N is involved in release of progeny virus. A is responsible for regular outbreaks, B is responsible for sporadic outbreaks (humans only), C is minor resp virus, not serious human pathogen. There are 16 subtypes of H and 9 subtypes of N. Antigenic variation occurs particularly with H. A B and C undergo antigenic drift, A in particular undergoes antigenic shift. Small changes are antigenic drift, causes heavier than usual flu season, sporadic outbreaks. Antigenic shift creates a new antigen with genetic reassortment, new subtype created. Causes sudden appearance of new H subtype, may be accompanied by changed N.
Pathogenesis is 1-2 day incubation, adherence to resp endothelium by H protein, there is receptor mediated endocytosis. Airborne transmission is affected by humidity, ventilation and UV radiation. More likely to spread indoors. Causes chills, fever, malaise, headaches, viral spread, recovery in 3-7 days or 1-3 weeks. Can cause secondary bacterial infection- in very young small airways can be blocked from inflammation, very old immune system declines. Death may result from pneumonia. Antivirals target N such as Oseltamivir which causes mild to moderate nausea and vomiting, can cause psychological effects in children. Should treat within 2 days of illness. Surveillance data helps determine vaccine.
Nocosomial infections are mainly bacteria, fungi, followed by viruses. Gram +ve are Staph aureus, Strep pyogenes, Enterococci (VRE). Gram -ve are E coli, Pseudomonas, Proteus, Enterobacter, Klebsiella. Protective asepsis should be used for immunocompromised and regular asepsis.