SH public health

List the 3 subtypes of influenza virus

influenza A, B, C

What is the incubation time for influenza virus?

1-4 days

Compare Influenza A & B, interms of the symptoms they cause

• Influenza A - sick for up to 3 weeks, potentially serious

• Influenza B - milder symptoms

Compare Influenza A & B, in terms of viral mutation

• A → genetic drift and shift

• B → drift only

Compare Influenza A & B, in terms of the impact they have

• A → can cause pandemic

• B → usually epidemics, less severe than A

Is Influenza C as serious as A and B?

only cause a very mild infection

How to distinguish influenza from common cold?

• fever, myalgia, abrupt onset

• unwell for longer periods

Which population is affected by influenza the most?

very young & old

Describe the socio-economic impact of the influenza virus

• large direct medical cost + indirect economic impact

• lost work days & earnings, loss of lives

Describe the general pattern of influenza infection

• repeated infections + rapid spread

• regular, short-lived epidemics, with occasional pandemics

What is the architecture of the influenza virus?

helical

The central part of the influenza virus is the nucleocapsid core. What does it contain?

• nucleoproteins

• single, negative-strand RNA

What is the function of nucleoproteins?

protect viral genome, facilitate replications

What does it mean when the virus have a single, negative-strand DNA?

needs transcription for translation to occur

Influenza virus express hemagglutinin and neuraminidase molecules (HA, NA) on the surface. What is their function?

facilitate attachment & insertion of viral materials

What is the function of the matrix found on the influenza virus?

stabilise envelope

What causes antigenic drift in viral evolution? What could be its impact and what subtype of influenza does this occur in?

• viral polymerase makes mistakes during replication → mutations + amino acid substitution.

• epidemic

• FLU A & B

What causes antigenic shift in viral evolution? What could be its impact and what subtype of influenza does this occur in?

• zoonosis + reassortment → new influenza HA subtypes

• no immunity in population → pandemics

• FLU A

Describe what reassortment is

• 2 different virusese infect the same cell → segmented RNA mix & reassort during replication → new variants

Describe the steps, how does influenza virus replicate?

1. attach to host cells → mediated by HA

2. viral membrane fuse with host cell membrane → release viral RNA

3. trascript to viral mRNA → host ribosomes translate into viral proteins

4. replicated viral RNA segments assemble with viral proteins

5. virions release via budding

What are the 3 conditions for a pandemic to emerge?

1. new inflluenza subtype

2. can infect human + serious disease

3. spread easily & sustainably among humans

Clinical diagnostic tools for influenza - the useful ones

PCR, RAT tests

What population in particular should be vaccinated against influenza at each flu season?

• >65 yo, immunodeficiency, >6 months with chronic medical condition

• women in 2nd/3rd trimester during flu season

Are antiviral treatments recommended for influenza?

not that effective

What is the rationale of vaccination?

• generate immunological memory safely

• infected at chosen times

How does vaccination work to protect people from secondary exposure?

• humeral response → antibodies + memory B cells → potent secondary response

When pathogen load exceeds the level of neutralizing antibodies, would there be infection?

yes but limited

What is herd immunity

• generate protection by vaccinating a sufficient number of ppl

• most transmission are blocked → vulnerable ppl are protected

What is ring vaccination

• vaccinate ppl with close contact to infected patient only

• prevent transmission via surrounding the patient with a ‘ring’ of immunisation

Does herd immunity and ring vaccination apply to all circumstances?

no

Generally what do antibodies and CD8 T cells target, respectively?

• antibodies → extracellular pathogens

• CD8 T cells -? intracellular pathogens

requirement of a successful vaccine

• safe, protective, sustained protection

• induce neutralising antibodies & T cells

• practical - low cost, easy to administer, few side-effects

What are tissue resident memory cells?

memory cells that sit in tissues at risk of infection

Successful vaccines have been developed against pathogens with certain characteristics. What are these characteristics?

• can be treated by antibodies

• stable antigen repertoire

What are some factors that may affect vaccine efficacy?

• demographic → circulating virus, community proximity, herd immunity

• host → age, cormorbidities, genes

• viral variant → antigen mismatch with vaccines

• immune → quality/amount/function of immune cells

• access

Define vaccine efficacy

researched under controlled conditions

Define vaccine effectiveness

measures the reduced infection risk among the vaccinated in the real world

Some pathogens have evolved to reduce their recognition and presentation by MHC II. What are some ways to overcome this>?

cojugated vaccines + adjuvants (vehicles & immunostimulants)

How do vehicles in adjuvants act?

display antigen * mimic pathogen, deposit antigen & increase their delivery to APC

How does immunostimulants in adjuvants act?

directly activate immune cells

Define virulence factors

• molecules on a pathogen

• enable it to cause disease

Define reservoir in terms of infectious disease

• place where infectious agent lives & multiplies

• source which other individuals can be infected

Define pandemic

• 1 infectious disease affecting large no. of ppl

• has spread over a few countries/worldwide

Define epidemic

• 1 outbreak, sudden increase in no. of disease cases

• above what is expected in the population

Define endemic

always present in a population or region

What does it mean when an infectious disease is sporadic?

occurs infrequently & irregularly

What is the requirement for an infectious agent to cause infection in a new host?

• it can survive in the environment

• enough of its kind will reach the new host

• it can establish colonies in the new host

What does the term ‘infective dose’ mean?

• no. of infectious agents required in the initial colony

• to cause infection in the new host

What are some types are tranmission?

• horizontal, vertical, zoonoses

• direct, indirect, air-borne

Define horizontal transmission

between members of same species

Define verticle transmission

from parental generation to offspring

Within the catgory of vertical transmission, there are 3 sub-catergories: in utero, intrapartum and postpartum. Define what they mean.

• in utero → in uterus via placenta

• intrapartum → during infant passage through birth canal

• postpartum → after birth, breatfeeding

Define zoonoses

from animal to humans

Define direct transmission

• susceptible host → physical contact with infected source

Define indirect route of transmission

infectious agents carried by the vector → susceptible host

Define vectors

• insects, animals, inanimate objects

• arthropods carrying virus

Define airborne route of transmission

• droplet & aerosol spread

• particle fall on inanimate surface → inhaled

How may infectious agent enter the host?

• mucosal surface → respiratory (inhalation), oral-faecal, venereal

• skin, blood

What are some factors that affect infectious disease transmission?

• pathogen

• host - genetics, immunity, travel, sexual behaviour

• environment - season, ventilation, geographic location

Aim of prevention for infection transmission

• reduce & eliminate source of infection

• prevent/reduce disease transmitting vectors