Influenza Flashcards
What is influenza (illness)?
- a contagious viral respiratory illness
What is the incidence of influenza worldwide?
- 3-5 million cases of severe illness
What is the make-up of the influenza virus?
- single-stranded family of RNA viruses referred to as Orthomyxoviridae
- classified as wither type A,B, or C
Influenza __ is responsible for up to 90% of epidemic influenza
A
What are the different subtypes within influenza A based on?
- based on the surface hemagglutinin (HA) or neuraminidase (NA) glycoproteins
Influenza __ has never been seen in humans
C
How is influenza spread?
- respiratory droplets caused by coughing and sneezing
When are most healthy adults able to infect others with influenza?
- 1 day before symptoms start and 5-10 days after becoming sick
What is the typical incubation period of influenza?
- 1-4 days (average 2 days)
The seasonal flu vaccine this year is a _____ vaccine
quadrivalent
What is the common clinical presentation of influenza?
- fever
- muscle pain
- headache
- non-productive cough
- malaise
- sore throat
- rhinitis
(these usually RESOLVE in 1 week of presentation - cough and malaise persist for more than 2 weeks)
What are the general complications of influenza vs a common cold?
Influenza: respiratory failure, especially with chronic conditions
Common cold: congestion, sinus or ear infection
Describe the complications of influenza?
- diffuse viral pneumonitis - the clinical syndrome most likely to result in hospitalization (can lead to shock and resp. failure)
- pneumonia - secondary bacterial infection
- dehydration
- worsening of concurrent medical conditions (asthma, diabetes, congestive HF)
- viral myocarditis is a rate complication
- acute coronary syndrome
- exacerbations of chronic pulmonary conditions
What are the bacteria that cause secondary bacterial pneumonia?
- staphylococcus aureus
- streptococcus pneumoniae
- hemophilus influenzae
- other gram negative bacilli
Samples for influenza testing include what?
- nasopharyngeal swab
- nasal wash
- nasal aspirate
- blood for antibodies
A viral culture provides test result in _____ days
3-10
Viral culture detects both influenza ___ and ___
A and B
What test is done that identifies the presence of influenza A and B viral nucleoprotein antigens in respiratory specimens, and display the result in a qualitative way (positive vs negative)
Rapid influenza diagnostic tests
What is the advantages of rapid influenza tests?
- produce quick result in 15 minutes or less
- simple to perform
- some RIDRs are approved for office/bedside use
What is the disadvantage of rapid influenza tests?
- sensitivity (10-69%) false negative results are common especially when influenza activity is high
- although specificity is high, false positives can also occur, especially during times when influenza activity is low
- Some RIDTs distinguish between influenza A or B virus infection while others do not. They do not provide information about influenza A subtypes or specific strain information
Describe serological testing
involves testing serum samples for influenza antibody to diagnose a recent infection. Two sample are collected, one within the 1st week of illness and the second 2-4 weeks later. If antibody levels are higher in the second sample than the first, it is likely that the influenza virus was present
Describe how neuramidase inhibitors work?
they bind to the protein of the virus and does not allow the virus to leave and spread throughout the body
- also cause clumping of the virons and do not allow them to spread
- 2 mechanisms that neuramidase inhibitors stop the spread
____ is extensively converted to its active metabolite by hepatic esterases (drug interactions involving competition for esterase have NOT been reported)
Oseltamivir
Clearance of oseltamivir carboxylate is by ______ and ______ by an anionic transporter system. Reduce the dose in renal impairment
glomerular filtration
tubular secretion
____ can decrease the renal excretion of the oseltamivir carboxylate
Probenacid
What are the most common side effects of oseltamivir?
gastrointestinal (nausea, vomiting, diarrhea) - mitigated by ingestion of food
What is the most concerning side effects of oseltamivir that is most commonly seen in children?
neurological adverse effects (kids being injured or killed by jumps or falls from buildings)
How is zanamivir administered?
- administered by dry powder inhaler (not orally bioavailable)
- severely limits zanamivir’s role in critical illness
Only about _______ of an inhaled dose of zanamivir is absorbed systemically?
10-20%
Is zanamivir significantly metabolized or excreted renally? What is the significance of this?
No
- significance is that there is no dosing adjustments needed in individuals with impaired renal or hepatic function
When oseltamivir is started within the first 4 days of treatment, what generally happens?
- there is a significant reduction in viral load than those that were left untreated
Minimal to no benefit was reported in healthy children and adults when antiviral treatment was initiated in _____
more than 2 days
When oseltamivir is started within the first 24 hours of illness onset, the median time to illness resolution was shortened by how long?
- by 3.5 days compared with placebo
Antiviral treatment is recommended as early as possible for any patients with confirmed or suspected influenza who is:
- hospitalized
- has severe, complicated or progressive illness
- at a higher risk of influenza complications
Antiviral treatment should be offered to persons at higher risk of influenza complications. These include what?
- children under 2 y/o
- adults over 65 y/o
- persons with chronic pulmonary, cardiovascular, renal, hepatic, hematological, metabolic disorders (including DM) or neurologic disorders
- persons with immunosuppression, including that cause by medications or by HIV infection
- women who are pregnancy or postpartum
- persons under 19 y/o who are receiving long term ASA tx
- First Nations people
- persons who are morbidly obese
- residents of nursing homes and other chronic care facilities
Combination therapy raises the promise of decreasing _______ and increasing efficacy of therapy. In actuality, however, oseltamivir-zanamivir combination actually _______
emergence of resistance
- impaired rate of recovery
IT IS COUNTERPRODUCTIVE
Higher doses of oseltamivir may have eradicated the virus faster, but they have no influence on ______
survival of the person
What is known to be the most effective method for preventing the season influenza virus infection and its complications?
- annual influenza vaccination
All people above what age are recommended to get an annual influenza vaccine?
6 months of age
With a good match influenza vaccination can prevent influenzal illness in _____ of healthy children and adults and ___ of the elderly
70-90%
50%
What is the preservative used in influenza vaccinations?
thimerosal
How long does it take for a person to develop immunity from a quadrivalent vaccine?
2 weeks
Explain the mechanism of vaccine protection?
IM administration of inactivated influenza vaccine results in the production of circulating IgG antibodies to the viral hemagglutinin and neuramidase, as well as cytotoxic T lymphocyte response
- both humoral and cell mediated responses are thought to play a role in immunity to influenza
- the antibody response after vaccination depends on several factors, including the age of the recipient, prior and subsequent exposure to antigens and the presence of immunodeficiency states
- humoral antibody levels are generally achieved within 2 weeks of immunization
Who should not get vaccinated?
- people who have had a previous anaphylactic reaction to any element of the vaccine
- people with IgE mediated hypersensitivity to eggs
- people who are currently experiencing a high fever (because if the fever worsens we do not know if the fever was from the vaccine or a prior illness
The influenza vaccine can inhibit the clearance of ____ and _____
warfarin
theophyllline
(have not shown any adverse effects however)
What are the most common adverse reactions to being vaccinated?
- mild symptoms developing soon after the vaccine and lasting for 1-2 days
- soreness, redness or swelling where the injection was given - severe breathing problems in minutes to hours in those with severe egg allergies
- CANNOT cause influenza b/c the virus is not live
- post vaccination fever may be observed in under 12% of immunized children aged 1-5 y/o
