Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
26 Cards in this Set
- Front
- Back
|
Influenza virus: structure
|
RNA Virus
Virulence Proteins -Hemagglutinin (H1-H15) -Neuraminidase (N1-N9) -M protein --Only on type A --Provides structure for an ion-pore channel Influenza A consists of various subtypes, grouped according to variations in HA & NA -5 HA subtypes (H1,H2,H3,H5 and H9) and 2 NA subtypes (N1,N2) have infected humans -H1,H2 and H3 subtypes have circulated globally -Outbreaks of H5 and H9 have occurred Influenza B only has one form of HA and one form of NA |
|
|
Antigenic drift
|
Small annual drift in minor determinants of H and N proteins
Occurs through a series of mutations, substitutions or deletions in amino acids constituting the hemagglutinin or neuraminidase surface antigens Occurs only after a particular viral strain has become established in humans Represents an adaptation to the development of host antibodies Newly developed antigenic strains prevail for a period of 2 to 5 years, only be to replaced by the next emerging strain (i.e. H1N1 Bangkok, H1N1 New Dehli) Influenza epidemics occur as a result of antigenic drift -Type A and Type B |
|
|
Antigenic shift
|
Large shifts in H or N subtypes by recombination
Occurs when type A influenza virus with a novel hemagglutinin or neuraminidase moves into humans from other host species Shifts occur less frequently than drifts More dramatic impact due to global immunologic susceptibility = PANDEMIC The influenza pandemics of 1957 and 1968 were caused by genetic reassortment between human and avian influenza A virus Influenza pandemics occur as a result of antigenic shift -Type A only |
|
|
Influenza pandemics and epidemics
|
A new virus (shown here as Type A HxNx) is introduced to a population that has no antibodies against it
Pandemic results Antibody formation increases after exposure Increased immunity applies evolutionary pressure Virus responds with variant strains (antigenic drift): epidemics Population develops widespread immunity after 10 years Selection pressures make the environment ripe for the spread of an entirely new virus: Type A HyNy (introduced by genetic reassortment or antigenic shift) The population has no immunologic protection: pandemic |
|
|
Majority of US influenza
|
The majority of influenza is due to two strains of type A influenza and one type B
-H3N2 (Type A) -H1N1 (Type A) -B In U.S. last year: -80% type A --60% was H3N2 --40% was H1N1 -20% type B |
|
|
Influenza clinical syndromes and complications
|
Febrile respiratory illness
Viral pneumonia Acute respiratory distress syndrome Secondary bacterial infections (particularly bacterial pneumonia) Hospitalization Death |
|
|
Novel H1N1 pandemic
|
Young children and young adults infected most
Young adults died most -Mortality due to immune response rather than virus Symptoms: -Fever -Cough -SOB (ominous sign) -Less myalgias and fatigue than normal |
|
|
Viral/bacterial interactions in influenza
|
Pathophysiological effects
-Destroyed/damaged physical barriers -Increased bacterial adherence (NA mediated) -Decreased mucociliary activity -PMN dysfunction After these effects, body is set up for bacterial infection -Where most of the mortality will occur -S. pneumoniae and S. aureus most common post influenza Influenza enhances pneumococcal virulence |
|
|
Antiviral drugs
|
Amantadine and rimantadine
-Type A --M protein inhibitors -Oral -Much resistance, not used anymore in clinical practice Oseltamivir -Type A and B --Neuraminidase inhibitor -Oral Zanamivir -Type A and B --Neuraminidase inhibitor -Inhaled |
|
|
Oseltamivir
|
Oseltamivir reduces the risk of hospitalization due to LRTI
Reduces risk of pneumonia by 55% (therefore reduces antibiotic use) Oseltamivir resistance: -2008: 8.6% H1N1 strains -1% pandemic H1N1 strains -Zanamavir still effective – more difficult to use |
|
|
Seasonal influenza vaccine: overview
|
Contains 3 strains of influenza viruses that are predicted to be the most common during the upcoming flu season: one influenza A (H3N2) virus, one influenza A (H1N1) virus, and one influenza B virus
Grown in eggs 2 types: -Inactivated (killed) -Live, attenuated |
|
|
Inactivated, killed influenza vaccine
|
Regular TIV
-IM -Approved for all persons ≥6 months (healthy, chronic medical conditions, pregnant women) High-dose TIV (FluZone High Dose) -IM -Contains 4x the amount of antigen -Approved for persons ≥ 65 yrs -Introduced in 2009 Intradermal TIV -Administered into the dermal layer of skin via microinjection syringe (90% smaller) -40% less antigen -Approved for persons ages 18-64 yrs -Introduced in 2011 |
|
|
Live, attenuated intranasal vaccine
|
Nasal spray
Used in healthy persons age 2-49yrs who are not pregnant |
|
|
Who should receive influenza vaccine
|
Everyone > 6 months should be vaccinated
-Children 6 months - 8 years need 2 doses for their first vaccination Vaccine contraindications: -People who have a severe allergy to chicken eggs -People who have had a severe reaction to an influenza vaccination -Children < 6 months of age --influenza vaccine is not approved for children in this age group -People who have a moderate to severe illness with a fever --wait until they recover -A h/o Guillain-Barré Syndrome (GBS) within 6 weeks following receipt of influenza vaccine |
|
|
Influenza vaccine side effects
|
TIV
-Large amount of safety data in children and adults -May cause injection site reactions (pain, redness, swelling) -Resolve within 2 days -Systemic events (low-grade fever, myalgia) may occur and may or may not be related to the vaccine -Vaccine contains inactivated virus and cannot cause influenza LAIV -Children --Rhinorrhea --Nasal congestion --Fever >100F --Wheezing -Adults --Rhinorrhea --Nasal Congestion --Sore Throat --Headache --Fatigue --Myalgias --Cough |
|
|
When to give influenza vaccine
|
October to November to cover peak flu season (Jan to March)
|
|
|
Influenza vaccine efficacy
|
Vaccine efficacy 50-90%
-Depending on year -Circulating strains -Host population 50-70% efficacy in older adults Reduces risk of: -Respiratory illness -Pneumonia -Hospitalization -Death Cost effective, reduction in: -influenza-like illness -MD visits -Hospitalization -lost workdays |
|
|
S. pneumoniae: disease, epidemiology
|
Major cause of:
-Bacteremia -Meningitis -Pneumonia -Sinusitis -Acute otitis media Primarily a disease of young and old |
|
|
Groups at risk for invasive pneumococcal disease
|
Chronic Heart Disease
Diabetes Mellitus Chronic Lung Disease Smokers -Even without lung disease -Includes passive smoke exposure Alcohol Abuse Immunocompromised -Malignancy -HIV infection -Asplenia -Sickle cell disease (functional asplenia) |
|
|
Pneumococcal vaccines: efficacy
|
Most effective in reducing invasive pneumococcal disease (IPD)
Moderately effective in reducing pneumoina Somewhat effective in reducing otitis media and related office visits |
|
|
Polysaccharide pneumococcal vaccine
|
PPVSV or Pneumovax®, 1983
Adults > 65 yrs Adults 19-64 yrs who smoke or have asthma Children ≥ 2 yrs and at high risk for disease (e.g., sickle cell disease, HIV infection, other immunocompromising conditions) Reduces the risk of IPD by ~70% Reduces mortality due to IPD |
|
|
Protein-conjugate pneumococcal vaccine
|
PCV7 or Prevnar 7®, 2000
PCV13 or Prevnar 13®, 2010 recommended for all children under 5 years of age Immunocompromised Adults Protein-conjugate vaccines are more immunogenic (90-98% efficacy), but contain fewer serotypes |
|
|
Pertussis: phases, vaccine
|
Classic pertussis: 3 phases, lasts 2-3 months
-Catarrhal: malaise, rhinorrhea, mild cough, low-grade temp, excessive lacrimation, conjunctivitis -Paroxysmal: coughing paroxysms, inspiratory whoop, post-tussive emesis, leukocytosis, lymphocytosis -Convalescent: cough less frequent, less severe Acellular pertussis vaccine reduces incidence -DTaP, used in children (85-95% efficacy) -Tdap, used in adults (92% efficacy) |
|
|
Haemophilus influenza: bacteria and vaccine
|
Encapsulated bacteria causing:
-pneumonia, bacteremia, epiglottitis, otitis media, sinusitis, meningitis Hib conjugate vaccine has been routinely used in infants and children since 1990 -Incidence of Hib disease has decreased by 99% Excellent safety profile |
|
|
Vaccination rates
|
Children 85-95% vaccine coverage
Adults -20% at risk for pneumococcal disease who have received a pneumococcal vaccine -20% received pertussis vaccine -40% received influenza vaccine |
|
|
Strategies to improve immunization rates
|
Standing orders: the single most effective strategy
Chart reminder: adds ~ 4 minutes to an office visit Computerized reminder system: needs programmer Mail/Telephone reminders: needs significant staff time Performance feedback: needs tracking system Expanded access settings: reaches those outside the medical system, may duplicate immunizations and no record within healthcare system Patients get immunized because provider tells them to. |
