MEDS 580 LECTURE 4 EXAM QUESTIONS
WITH DETAILED VERIFIED ANSWERS
influenza virology
enveloped RNA virus with surface projections of hemagglutinin (H or HA) and neuraminidase
(N or NA)
influenza A
16 highly divergent, antigenically distinct HAs, least nine distinct NAs (N1 to N9)
influenza B
similiar structure to influenza A, do not exhibit teh same type of antigenic and genetic variation
in the HA and NA, do not have subtypes
influenza virology pt 2
segmented genome, A and B each have 8 segments, reassortment which allows segments to be
exchanged between viruses infecting the same cell
Reassortment
segments can be exchanged between viruses infecting the same cell, important for the formation
of pandemic viruses
antigenic drift
relatively minor changes that happen in NA and HA, due to amino acid changes given that RNA
viruses have poor genetic proof reading mechanisms when replicating
antigenic drift effects
antibody generated by exposure to previous strains does not neutralize the antigenic variant as
effectively, previous exposure provides protection to an extent, main reason why people get the
flu more than once
antigenic shift
,radical changes in antigenicity of HA or NA, results in new HA or Na proteins, ONLY occurs in
influenza A, responsible for pandemics, source of new genetic material is in flu viruses affecting
other animals such as birds or swine
seasonality of flu
in temperate zones, colder winter months, low temp and low humidity, low levels of ultraviolet
radiation, close congregation of people in domestic dwellings with low ventilation
epidemic influenza
influenza A/H3N2 in 1976, confined in one location, began abruptly, reached sharp peak in 2 to
3 weeks, lasted 5 to 6 weeks
epidmeic influenza indicators
reports of increased numbers of kids with febrile respiratory illness followed by illness among
adults, followed by increased hospital admissions, followed by absenteeism in school and
industrial settings, increased deaths from pneumonia, increased internet searches for flu
pandemic influenza metrics
Novel/new influenza A virus unrelated to the circulating pre pandemic virus must emerge and
circulate among people, little to no pre-existing immunity in the global population to the new
virus, cause significant illness, spread efficiently from person to person
reasons pandemic flu can occur
virus has segmented genome(reassortment), influenza A viruses, not other viruses, maintain a
large reservoir of genetic diversity primarily in birds(antigenic shift)
avian influenza
is a disease of birds caused by the influenza A virus, ducks and geese are primary reservoir
pandemic virus subtypes from birds
subtypes containing all 16 known haemagglutinin and nine neuraminidase antigens are known to
occur in wild birds
, pandemic viruses from birds
influenza viruses have been detected in a range of bird species, from wild aquatic shore birds to
domestic poultry, likely source of the 1918 Spanish Flu Pandemic
pandemic mode 1
pigs have receptors for both avian and human influenza viruses. A doubly infected pig may
select a reassortant virus that could infect and spread among people
pandemic mode 2
man could be infected with an avian influenza virus. Through accumulations of point mutations
(genetic adaption) a variant could arise that could spread efficiently from person to person. This
mode was probably the mechanism behind the appearance of the Spanish influenza
pandemic mode 3
man could simultaneously be infected with both avian and human influenza viruses. A
reassortant virus could be selected that could infect and spread among people. So far not a
documented pandemic mode, but human-human reassortants have been documented
Low pathogenic avian influenza (LPAI)
infected birds generally are healthy and remain infected for about 1 month, during which time
the virus replicates in the GI tracy and is excreted in high levels in feces. Symptoms include
decreased egg production, reduced appetite, ruffled feathers, swollen heads, mild respiratory
symptoms
Highly pathogenic avian influenza (HPAI)
rapidly spreading outbreaks with high mortality, birds often die same day symptoms appear,
respiratory symptoms plus internal hemorrhaging
HPAI subtypes
Only A/H5 and A/H7, characteristic set of basic amino acids in the HA cleavage site which
differentiates them from all other avian influenza viruses and is associated with their high
virulence and mortality rate
WITH DETAILED VERIFIED ANSWERS
influenza virology
enveloped RNA virus with surface projections of hemagglutinin (H or HA) and neuraminidase
(N or NA)
influenza A
16 highly divergent, antigenically distinct HAs, least nine distinct NAs (N1 to N9)
influenza B
similiar structure to influenza A, do not exhibit teh same type of antigenic and genetic variation
in the HA and NA, do not have subtypes
influenza virology pt 2
segmented genome, A and B each have 8 segments, reassortment which allows segments to be
exchanged between viruses infecting the same cell
Reassortment
segments can be exchanged between viruses infecting the same cell, important for the formation
of pandemic viruses
antigenic drift
relatively minor changes that happen in NA and HA, due to amino acid changes given that RNA
viruses have poor genetic proof reading mechanisms when replicating
antigenic drift effects
antibody generated by exposure to previous strains does not neutralize the antigenic variant as
effectively, previous exposure provides protection to an extent, main reason why people get the
flu more than once
antigenic shift
,radical changes in antigenicity of HA or NA, results in new HA or Na proteins, ONLY occurs in
influenza A, responsible for pandemics, source of new genetic material is in flu viruses affecting
other animals such as birds or swine
seasonality of flu
in temperate zones, colder winter months, low temp and low humidity, low levels of ultraviolet
radiation, close congregation of people in domestic dwellings with low ventilation
epidemic influenza
influenza A/H3N2 in 1976, confined in one location, began abruptly, reached sharp peak in 2 to
3 weeks, lasted 5 to 6 weeks
epidmeic influenza indicators
reports of increased numbers of kids with febrile respiratory illness followed by illness among
adults, followed by increased hospital admissions, followed by absenteeism in school and
industrial settings, increased deaths from pneumonia, increased internet searches for flu
pandemic influenza metrics
Novel/new influenza A virus unrelated to the circulating pre pandemic virus must emerge and
circulate among people, little to no pre-existing immunity in the global population to the new
virus, cause significant illness, spread efficiently from person to person
reasons pandemic flu can occur
virus has segmented genome(reassortment), influenza A viruses, not other viruses, maintain a
large reservoir of genetic diversity primarily in birds(antigenic shift)
avian influenza
is a disease of birds caused by the influenza A virus, ducks and geese are primary reservoir
pandemic virus subtypes from birds
subtypes containing all 16 known haemagglutinin and nine neuraminidase antigens are known to
occur in wild birds
, pandemic viruses from birds
influenza viruses have been detected in a range of bird species, from wild aquatic shore birds to
domestic poultry, likely source of the 1918 Spanish Flu Pandemic
pandemic mode 1
pigs have receptors for both avian and human influenza viruses. A doubly infected pig may
select a reassortant virus that could infect and spread among people
pandemic mode 2
man could be infected with an avian influenza virus. Through accumulations of point mutations
(genetic adaption) a variant could arise that could spread efficiently from person to person. This
mode was probably the mechanism behind the appearance of the Spanish influenza
pandemic mode 3
man could simultaneously be infected with both avian and human influenza viruses. A
reassortant virus could be selected that could infect and spread among people. So far not a
documented pandemic mode, but human-human reassortants have been documented
Low pathogenic avian influenza (LPAI)
infected birds generally are healthy and remain infected for about 1 month, during which time
the virus replicates in the GI tracy and is excreted in high levels in feces. Symptoms include
decreased egg production, reduced appetite, ruffled feathers, swollen heads, mild respiratory
symptoms
Highly pathogenic avian influenza (HPAI)
rapidly spreading outbreaks with high mortality, birds often die same day symptoms appear,
respiratory symptoms plus internal hemorrhaging
HPAI subtypes
Only A/H5 and A/H7, characteristic set of basic amino acids in the HA cleavage site which
differentiates them from all other avian influenza viruses and is associated with their high
virulence and mortality rate
