Influenza Flashcards
1
Q
Influenza peak season
A
- winter through spring
- october –> may
2
Q
Influenza virus general structure
A
- segmented ssRNA (x8)
- lipid envelope around core
- matrix protein on inner surface
- 2 main surface viral proteins: hemagglutinin (H) and neuraminidase (N) glycoproteins
- different H or N proteins designated by numbers (H1, H2, N1, N2, etc.)
3
Q
Types of influenza virus
A
- 3 main types: A, B, C
- A & B more common, C is mild
- A=epidemics and pandemics, and can infect other animals
- B=generally milder, human only
4
Q
Nomenclature of influenza viruses
A
- Virus type + Geographic origin + strain number + year of isolation + virus subtypes
- e.g. A/Moscow/21/99 (H3N2)
5
Q
Antigenic drift definition
A
- gradual change in virus through slow accumulation of mutations in H and N antigens
- only after established in humans
- adaptation to human Abs
6
Q
Antigenic shift definition
A
- type A influenza virus w/completely novel H or N gene introduced into humans
- new gene segment acquired from other host species
- gene reassortment when two or more influenza viruses infect single human or animals
- pigs often serve as “mixing vessel” –> e.g. “swine flu” (2009 H1N1)
7
Q
Pandemic H1N1 origin
A
- influenza virus w/gene segments of human, avian, and swine strains
- created via reassortment/antigenic shift
- first noted in March 2009 in Mexico, then US and Canada
8
Q
Pandemic H1N1 epidemiology
A
- began in North America in March 2009
- widespread community transmission of Pandemic H1N1 on at least two continents
- highest among children and young adults 65
9
Q
Pandemic H1N1 morbidity/mortality
A
- est. 60 million US cases
- 270,000 hospitalizations
- 12,000 deaths
10
Q
General contents of influenza vaccines
A
- same 3 strains of influenza
- two “A” strains and one “B” strain–predicted to be circulating next season–are selected for trivalent
- additional “B” strain added to quadrivalent
11
Q
Major types of influenza vaccine
A
- Inactivated influenza vaccine (TIIV) = injectable, killed vaccine. >6 mos. trivalent and quadrivalent available.
- Live attenuated influenza vaccine (LAIV, FluMist) = intranasal delivery of live, weakened virus. healthy 2-49 yrs, not pregnant or immunocompromised. quadrivalent.
12
Q
Effective influenza prevention
A
- vaccination: TIV=70-90% effective
- hand hygiene
13
Q
CDC influenza vaccine recommendations
A
- all people >6 mo. w/out contraindications
- all people in close contact w/infants
- high risk groups: pregnant women, children 65, chronic medical conditions, medical prof./caregivers
14
Q
Main criteria for a pandemic (3)
A
- emergence of a new influenza subtype
- virus must infect humans and cause serious illness
- virus must have sustained human-to-human transmission and spread easily among humans
15
Q
Main virulence acquisition methods for pandemic-causing viruses
A
- mutation or reassortment w/in a “mixing vessel” (e.g. pig) where human H gene assorts w/avian segments to produce novel strain
- non-human flu gains ability to bind human receptors: e.g. mutation in avian virus (binds alpha-2,3 linkage) allows binding of human receptor (binds alpha-2,6 linkage)
