Lec 26 Influenza Flashcards
What is uncomplicated influenza?
- acute, self limited
- febrile
- due to URI by influenza A or B
What are most common symptoms of uncomplicated influenza
- fever
- cough
- malaise
What symptoms separate influenza from common cold?
systemic symptoms
- fever +/- chills
- headache, myalgias
- malaise, anorexia
both can have:cough, sore throat, rhinorrhea
sneezing more frequent with common cold than flu
What is onset of flu systemic symptoms? how long do they last? Compared to respiratory?
systemic: abrupt onset, last for first 3 days of illness
respiratory: 7-8 days, persist or worsen after resolution of systemic symptoms
What are the respiratory symptoms of flu?
- dry cough, sore throat, rhinorrhea
- usually sneeze more frequent with common cold than flu
What are the 2 pulmonary complicationf of influenza?
- primary viral pneumonia
- secondary bacterial pneumonia
- acute exacerbation of asthma or COPD
What is primary viral pneumonia / signs of disease?
- extension of URI into URI
- monophasic illness:
- — starts like typical influenza but instead of getting better develop symptoms of pneumonia [dyspnea, hypoxemia, cyanosis +/- hemoptysis]
- CXR shows diffuse, bilateral/multilobar opacities
Who is at most risk for primary viral pneumonia?
- CV diseases [esp rheumatic disease with mitral stenosis]
- elderly esp w/ chronic CV or pulmonary comorbidities
- pregnant
- immunosuppressed
What is the most rare but most severe complication of influenza?
primary viral pneumonia
What is secondary bacterial pneumonia?
- bacterial pneumonia following seemingly uncomplicated influenza
- biphasic illness
- — initial improvement after typical influenza, then 4-14 days later have bacterial pneumonia symptoms [fever/chills, cough with sputum, dyspnea, pleuritic chest pain]
- crx: lobar/focal consolidation
What are the bacterial pathogens associated with secondary bacterial pneumonia?
- strep pneumo
- staph aureus
- less commonly: haemophilus influenza
Who is at risk for complicated influenza?
- older adults
- chronic pulmonary, cardiac, metabolic, or renal disease
What is effect of acute exarcebation of asthma or COPD related to viral influenza?
- very common
- may result in permanent decrease in pulm function
What are the non-pulmonary complications of influenza?
- myositis and myoglobinuria [in childrens]
- myocarditis and pericarditis, MI [mostly with pre-existing cardiac disease]
- toxic shock syndrome
- guillan-barre, tranverse myelitis, encephalitis
- reye’s syndrome
Whos is at most risk for reye’s syndrome?
kids taking aspirin
What are complications of influenza in pregnancy?
- fetal loss + pre-term labor
- neural tube defects
What is structure of influenza?
- family orthomyoviridae, genera A, B, C
- negative sense
- segmented
- enveloped
- RNA
What is nucleoprotein NP in influenza?
- binds genomic viral RNA
- NP + vRNA = ribonucleoprotein complex [RNP]
- genetically stable protein across strains
- target of most diagnostic tests
What is algorithm for diagnosing influenza clinically? who does it not work as well for?
flu season + fever + cough = influenza = 60-80% sensitive, 55-80% specific not as good of a marker in: - elderly/immunosuppressed/comorbid - young children
how is influenza diagnosed besides clinical symptoms?
- rapid influenza diagnostic testing [RIDT] = usually enzyme immunoassay for NP
- direct fluorescent antigen [DFA] test = best test
- nucleic acid amplification test [NAAT]
