Influenza Flashcards
Describe the shape and parts of the influenza virus
Enveloped, ssRNA virus consisting of 8 RNA fragments
What is the definition of a true influenza?
an acute infectious disease caused by a member of the orthomyxovirus family
How many types of RNA influenza viruses are there?
3
What are the three types of influenza virus and where are they found?
Influenza virus A- found in humans and animals
Influenza virus B- found in humans only and no change in external antigens
Influenza virus C- found in humans only
How are the different types of influenza virus determined?
By the internal antigens that are type-specific proteins
Major influenza outbreaks are associated with which viruses?
A and B
Which has a milder infections…type A or B?
Type B
The viral envelope of influenza A has which external antigens and these cause what?
external antigens HA and NA show more variation and are the subtype and strain-specific antigens
What is antigenic drift?
Due to mutation, after a few years strains may accumulate sufficient changes that an individual immune to the original strain in not immune to the drifted one
What is an antigenic shift?
Antigenic shift is due to a reassortment of antigens in influenza A
If both antigens shift in an influenza what can happen?
little immunity and an epidemic/pandemic is seen. This can also happen if only 1 antigen shifts
The all of the HA and NA antigens for influenza are seen in?
All 16 HA and 9NA types circulate in ducks, some also circulate in other animals
Influenza, animals, people…what can happen?
It appears that some animal, somewhere, becomes infected with both a human and an animal virus, and that one of the reassortants contains genes for human internal components but a new HA and/or NA segment from the animal virus
How is the influenza virus spread?
person to person via small particle aerosols
How long is the incubation period for the influenza virus?
24-48hrs
Fatalities are in which 2 groups from the influenza virus?
Elderly and children
Why are there fatalities in the elderly from the influenza virus?
Elderly have underlying decreased effectiveness of the immune system and/or chronic obstructive pulmonary disease or chronic cardiac disease
Why are there fatalities in children from the influenza virus?
No antibodies and the small diameter of components of the respiratory tract
What are the pathologies in the lungs from the influenza virus?
Respiratory cells die and efficiency of ciliary clearance is reduced; there is clearance of infectious agents from the respiratory tract
What are the symptoms of the influenza virus?
Fever(38-40 degrees C)
Myalgias(muscle pain), headache
Ocular symptoms-photophobia, tears, ache
Dry cough, nasal discharge
What are the 3 pulmonary complication with influenza?
Croup in children, primary influenza virus pneumonia, secondary bacterial infection
What is the non-pulmonary complication with influenza virus?
Reye’s syndrome
What is Reye’s syndrome and what is its origin?
Rare encephalitis, approximstely 40% of cases are fatal, the origin of Reye’s syndrome is unclear but seems to follow certain viral infections(influenza or chicken pox) especially in children treated with aspirin
What are 2 treatments for influenza and what do they do?
1) Amantadine- impairs the ability of the virus to attach to cells
2) Relenza and Tamiflu- prevent new virus particles from being released
How often are new vaccines made for the influenza virus?
A new vaccine is formulated annually with the types and strains of influenza predicted to be the major problem for the year. It has a short lived protective effect, given in the fall so that protection is high in December/January
What is a potential complication with the influenza vaccination? How frequent is it?
Guillain-Barré syndrome- body attacks its own nerve cells
One study suggested that one person out of a million vaccinated persons may be at risk of GBS associated with influenza vaccine
