influenza (quiz 1, exam 1) Flashcards
epidemiology
influenza virus infeciton is common: __% of the population infected each season; an average of __ annual influenza associate deaths in the US
- 10-20%
- 50,000
epidemiology
most influenza related mortality occurs indirectly as a result of complications of influenza, and the 2 main complications are _
- secondary bacterial pneumonia (including post-influenza MRSA pneumonia)
- cardiovascular compromise in pts with preexisting congestive heart failure (CHF) or coronary artery disease (CAD)
epidemiology
influenza infection occurs via __
aerosolized secretions (in conctrast with rhinoviruses/cold viruses, which are usually spread via fomites)
epidemiology
annual variation in the __ (3) enables influenza viruses to evade antibodies developed during previous seasons form infection or vaccination
- glycoproetines
- hemagglutinin (HA)
- neuraminidase (NA)
epidemiology
the usual mechanisms of antigenic variation, occuring in both influenza A and B, is referred to as
antigenic drift
epidemiology
antigenic drift occurs through constant and ongoing small mutation of __(2) during __
- HA (hemagglutinin) and NA (neuraminidase)
- the replicaiton cycle of the virus
epidemiology
people previously infected by strains differing by antigenic drift often have some antibody __ with the new strain, and are more likely to have __ illness
- cross-reactivity
- milder
epidemiology
antigenic shift only occurs in
influenza A
epidemiology
antigenic shift definition
an abrupt and major change via gene re-assortment resulting in a new HA (hemagglutinin) or NA (neuraminidase)
epidemiology
__ cross-reactivity exists between previous strains and new strains of influenza A occurring via antigenic shift
little or no
epidemiology
new strains occuring via antigenic __ have been responsible for global influenza epidemics and pandemics including __ (2)
- shift
1. 2009 influenza A H1N1 swine-origin influenza pandemic
2. 1918 Spanish flu (40 million people worldwide died)
epidemiology
multiple strains of influenza A exist within __ populations, most of which __ transmissiable to humans
- fowl
- are not
epidemiology
one strain that is highly pathogentic to fowl and has been transmitted to humans is __ influenza A (__)
- avian
- H5N1
__ is an exceedingly rare zoonotic infection spread by contact with birds
avian influenza A (H5N1)
epidemiology
symptoms of avian influenza A (H5N1) include __(3) preceding pneuomonitis by an average of __ days; pneumonitis may progress radpidly to __ and __
- fever
- watery diarrhea
- leukopenia
- 7 days
- respiratory distress
- acute respiratory distress syndrome
epidemiology
__ could adapt avain influenza A (H5N1) to adapt it to a human host and to human to human transmission
minor genetic changes
clinical features
infection with the influenza A and B viruses cause a spectrum of disease, from __ to __
- asymptomatic
- serious systemic illness
clincial features
symptoms usually occur after an incubation period between __ and __ hours (peak of __)
- 18 and 72 hours
- viral titer
clinical features
the virus titer then declines rapidly (after the peak at __ hours) and is no longer detectable within __ to __ days of initial infection
- 18-72 hours
- 5-10 days
clinical features
risk of contagion is believed to be minimal __ days after symptom onset in otherwise healthy pts
7 days
clinical featues
viral carriage and shedding maybe much longer in indivuduals with __
compromised immunity
symptoms
classically begin with abrupt onset of __ and __ such that the hour of __ may sometimes be pinpointed
- fever
- malaise
onset
symptoms
7 main symptoms
- fever, with or without rigors
- mayalgias (often of the back and large muscels in the extremities)
- malaise/lethargy
- non-productive cough and sore throat
- delirium
- rash
7, abdominal pain, diarrhea
symptoms
older individuals may present with fever, chills, and malaise without any __ complaints; also eldery pts can present with __ and __ without fever or respiratory symptoms
- respiratory
- lassitude
- confusion
symptoms
fever > __ and __ in infuenza season is highly predective of influenzza infeciton in those >__yo
- 38C (100.4F)
- cough
- 4yo
clinical findings
7 main ones
- flushed face and toxic appearance
- hyperemic mucosal membranes
- clear naseal discharge
- tender lymphadenopathym (esp. neck)
- rales or rhonchi may be auscultated in few than 20% of cases
- dehydration and orthostaic hypotension may also be present
- epithelial necrosis leading to bacterial superinfection (esp. with pneumococcus or S. aureus)
Diagnosis
usually __ (aka presumptive), __ tests, and __ and __ in areas of epidemic (positive predictive value of __%)
- clinical
- rapid Ag tests (nasal/pharyngeal)
- fever and cough
80%
influenza vs. common cold
fever
- URI: low grade or absent
- influenza: common
influenza vs. common cold
myalgias
- URI: absent
- influenza: common
influenza vs. common cold
rash
- URI: absent
- influenza: seen in 5-10% of pts
Differential diagnosis
__ is on the DDx for any pt with a cough and fever
bacterial pneumonia
DDx
a __ pulmonary parenchymal response represented by a __ cough, __ on auscultation, and __ visible on chest radiography help to distinguish bacterial pneumonia from influenza
- purulent
- productive
- consolidation
- inflitrates
clinical course
typical duration of severe symtpoms is __ to __ days, but can be (very rarely) more than __ days in healthy adults
- 3-4 days
- 7 days
clinical course
pts with compromised immune systems may have an extended duration of __ and __
- symptoms
- viral shedding
clinical course
history, symptoms, and physical exam can differentiate influenza A from influenza B
false
clinical course
complications tend to occure more frequently with influenza __
A
clinical course
influenza __ may cause more abdominal and gastrointestinal symptoms
B
diagnosis
influenza season occurs from __ to __ in the northern hemisphere, although the peak of activity in any area genreally lasts less than __ weeks
- october to april
- 6 weeks
diagnosis
during the peak activity, over __% of pts with fever and cough have influenza
30%
diagnosis
influenza is exceedinly rare during the __ season
-summer
diagnosis
the standard laboratory diagnosic method is a __ for viral antigen
rapid immunologic test (e.g. EIA)
diagnosis
__ is the most sensitive method and is replaceing viral culture
RT-PCR
diagnosis
__ is rapid and has 40-80% snesitivity when compared to __, which takes 5-7 days
- EIA
- viral culture
diagnosis
given the low sensitivity of immunologic tests for viral antigens, __ is becoming a standard diagnostic approach
RT-PCR
treatment
class of antiviral drug that treats influenza A only (2)
- adamantines: high levels of resistance to these and tehrefore are NOT USED
- rimantadine
treatment
class of antiviral drug that treats influenza A and B
neuraminidase inhibitors
treatment
adamantines is an antiviral drug class used to treat influenza __
A (not used though because high levels of resistance to these)
treatment
rimantadine is an antiviral drug class used to treat influenza
A
treatment
neuraminidase inhibitors is an antiviral drug class used to treat influenza __
A and B
treatment
oseltamivir (Tamiflu): is what type of drug class, dosing/duration, ages, comments
- neuraminidase inhibitor (treats influenza A and B)
- 75mg, 2x daily, for 3-5 days (within 48 hours)
- infants to adults
- infant to 12yo dose based on weight; N/V side effects; reduced dosing in pts with CKD
treatment
zanamivir (Relenza): drug class, dosing/duration, ages, comments
- neuraminidase inhibitor (treats influenza A and B)
- 10 mg, 2 inhalations, 2X daily for 3-5 days withing 48 hours
- greater than 7yo
- inhaler; side effects in contraindicated in asthma and COPDS
treatment
peramivir: drug class
- neuraminidase inhibitor (treats influenza A and B)
- available for emergencies with severly ill pts
treatment
neuraminidase inhibitors function by inhibiting viral __; they reduce the duration and severity of __ and the duration of __
- propagation
- symptoms
- viral shedding
treatment
antivirals must be started __ to provide clinical benefit in otherwise healthy adults because the majority of viral __ occurs __ in influenza
- early
- reproduction
- early
treatment
first dose should be givin within __ of symptom onset; after __ there is limited evidence of benefit among pts with intact immune systems
- 24 hours
- 48 hours
treatment and prevention
CDC reecommnedation of anativiral treatment for any individual with suspected or confirmed influenza who (3/f)
- is hospitalized
- has sever, complicated or progressive illness
- is at high risk for influenza complication
a. less than 2 yo or greater than 65 yo
b. chronic pulmonary, cardiac, renal, hepatic, hematologic, or metabolic disease
c. immunosuppression including HIV
d. pregnant women
e. BMI>40
f. resident in nursing home
treatment
prophylazix: duration of drug use, when used
- usually 7 days
- used during the week of peak influenza activity
treatment
criteria for selecting pts for immunoprophylaxis include (4)
- persons at high risk for influenza who were vaccinated after teh onset of an influenza outbreak
- persons with significant immune deficiency during an outbreak
- individuals unable to receive influenza vaccinations due to contraindications
- for control of an outbreak in a chronic care institution
prevention
4 ways to prevent influenza
- vaccination
- good hand hygeine
- unclear wheter facemasks are effective at reducing risk
- respirator masks (N95) filter 95% of airborne particles; should be worn by helath care professionals when caring for pts with suspected influenza
complications
secondary bacterial pneumonia organisms are typically these 3
- Streptococcus pneumonia
- Haemophilus influenza
- Staphylococcus aureus
complications
__ pneumonia is uncommon without preceeding influenza infection
Staphylococcus aureus
complications: secondary bacterial pneumonia
__, particularly __, is the most improtant pathogen to consider because it can cause a rapidly progressive necrotizing pneumonia and requires selection of antibiotics not usually used for community acquired pneumonia
- Staphylococcus aureus
- community acquired methicillin resistant S. aureus (CA-MRSA)
complications: secondary bacterial pneumonia
the pattern of secondary bacterial pneumonia usually follows a cours of __
initial improvement in symptoms and resolution of fever followed by clinical decline 4-10 days later
Influenza pneumonia with progression over 1wk
A. poorly defined nodular opacities and small areas of consolidation in the right middle and lower lung zones
B. extensive bilateral consolidaiton and poorly defined nodular opacities; also noted are an endotracheal tube and central venous line
complications
influenza infection also increases the risk for __ mortality, including death from __, __, and __
- caradiovascular
- stroke
- myocardial infarction
- congestive heart failure
complications
cardiac mortality associated with influenza is highest among individuals greater than __yo
60yo
