EXAM 2 PATH 1000 EXAM QUESTIONS AND ANSWERS WITH
COMPLETE SOLUTIONS
Types of influenza
Type A
Type B
Type C
Type D
Type A influenza
Mainly avian, also infect swine, humans, horses, and occasionally cats, mink, seal, and
whales
Wild aquatic birds, including gulls, terns, and shorebirds, and wild waterfowl, such as
ducks, geese, and swans are considered reservoirs (hosts) for avian influenza A viruses
Type B, C, and D influenza
Type B and C
Antigenically B and C are in humans only
Type D
Closely related to C seen in Cattle but significant is not cleared yet
Taxonomy and classification of influenza
Taxonomy and Classification
Family: Orthormyoviridae
Pleomorphic negative stranded RNA virus
Mutation rate: ~10^5.5 / replication
,Morphology flu (shape/size)
Virions are roughly spherical with diameter of 80-120nm
Surface spikes are hemagglutinin (HA) (rod) neuraminidase(NA) (mushroom)
Champion at genetic variation
Single- Stranded, negative sense RNA
Segmented genome: Causes Reassortment
8 segments, 1 or 2 proteins per segment (Encodes 10 or 11 proteins)
Almost all genes have been blames for host specificity and virulence at some time
IAV genome
divided into eight segments that encode 11 viral proteins in total (HA, NA, M1, M2, NP,
NS1, NS2, PA, PB1, PB2, and PB1-F2). The viral envelope of IAV contains the
transmembrane proteins HA, NA, and M2.
History of flu
Fowl plague in Italy 1878-1901
1950-1960 discoveries - Fowl plague virus
1955 demonstrated the virus called type A is influenza virus
1959 - H5N1 and 1961 - H5N3 in Scotland
1975 Australia Outbreak
England 1979, USA & Ireland 1983-84 outbreaks related to H5N2 serotype
Mexico 1994-95 (H5N2)
Pakistan H7N3 Australia H7N3 in 1994
California H7N2 in 2002-2003
Southeast Asia and China (H5N1-Bird Flu) 2003-2006 in southeast Asia
,Influenza A Viruses (subtypes)
Influenza A viruses are divided into subtypes on the basis of two proteins on the surface
of the virus:
hemagglutinin (HA) and neuraminidase (NA).
hemagglutinin (HA) and neuraminidase (NA).
There are 18 known HA subtypes and 11 known NA subtypes.
In birds, 16 HA and 9 NA subtypes have been identified. (Two additional subtypes,
H17N10 and H18N11, have been identified in bats.)
Many different combinations of HA and NA proteins are possible. (18x11=198
combinations)
For example, an "A(H7N2) virus" designates an influenza A virus subtype that has an
HA 7 protein and an NA 2 protein. Similarly, an "A(H5N1)" virus has an HA 5 protein
and an NA 1 protein.
antigenic drift
Flu virus surface proteins (HA and NA) can change in two ways. Antigenic drift and shift.
Flu viruses change all the time due to antigenic drift, but antigenic shift happens less
frequently
Antigenic Assortment
Viral segmented genome reassortment in mixed infections
256 genetically assorted progeny viruses
Genetic reassortment between human and avian viruses
Global cycle of avian influenza in animals
Reassortment
, (antigenic shift; how pandemic viruses are born)
Schematic presentation of putative "mixing vessel" host species
Schematic presentation of putative "mixing vessel" host species (pigs, quails, turkeys,
humans) which express sialic acid receptors for both avian- and human adapted
influenza A viruses (IAV) in their respiratory tracts. Hence, they are considered
susceptible for a wider range of IAV of different host origins. Co-infections with different
IAV create reassortment opportunities increasing the likelihood of the formation of
reassortants with increased zoonotic or pre-pandemic propensity
Disease in Poultry (LP and HP)
Low Pathogenic
-Subclinical infection
-Primarily respiratory
-Decreased egg production
Highly pathogenic
-100% mortality rate within 24 hours of exposure (no time for clinical signs to develop)
Clinical signs of influenza
Incubation period: 3-14 days
Birds found dead
Drop in egg production
Neurological signs
- Depression, anorexia, ruffled feathers
Combs swollen, cyanotic
Conjunctivitis and respiratory signs
COMPLETE SOLUTIONS
Types of influenza
Type A
Type B
Type C
Type D
Type A influenza
Mainly avian, also infect swine, humans, horses, and occasionally cats, mink, seal, and
whales
Wild aquatic birds, including gulls, terns, and shorebirds, and wild waterfowl, such as
ducks, geese, and swans are considered reservoirs (hosts) for avian influenza A viruses
Type B, C, and D influenza
Type B and C
Antigenically B and C are in humans only
Type D
Closely related to C seen in Cattle but significant is not cleared yet
Taxonomy and classification of influenza
Taxonomy and Classification
Family: Orthormyoviridae
Pleomorphic negative stranded RNA virus
Mutation rate: ~10^5.5 / replication
,Morphology flu (shape/size)
Virions are roughly spherical with diameter of 80-120nm
Surface spikes are hemagglutinin (HA) (rod) neuraminidase(NA) (mushroom)
Champion at genetic variation
Single- Stranded, negative sense RNA
Segmented genome: Causes Reassortment
8 segments, 1 or 2 proteins per segment (Encodes 10 or 11 proteins)
Almost all genes have been blames for host specificity and virulence at some time
IAV genome
divided into eight segments that encode 11 viral proteins in total (HA, NA, M1, M2, NP,
NS1, NS2, PA, PB1, PB2, and PB1-F2). The viral envelope of IAV contains the
transmembrane proteins HA, NA, and M2.
History of flu
Fowl plague in Italy 1878-1901
1950-1960 discoveries - Fowl plague virus
1955 demonstrated the virus called type A is influenza virus
1959 - H5N1 and 1961 - H5N3 in Scotland
1975 Australia Outbreak
England 1979, USA & Ireland 1983-84 outbreaks related to H5N2 serotype
Mexico 1994-95 (H5N2)
Pakistan H7N3 Australia H7N3 in 1994
California H7N2 in 2002-2003
Southeast Asia and China (H5N1-Bird Flu) 2003-2006 in southeast Asia
,Influenza A Viruses (subtypes)
Influenza A viruses are divided into subtypes on the basis of two proteins on the surface
of the virus:
hemagglutinin (HA) and neuraminidase (NA).
hemagglutinin (HA) and neuraminidase (NA).
There are 18 known HA subtypes and 11 known NA subtypes.
In birds, 16 HA and 9 NA subtypes have been identified. (Two additional subtypes,
H17N10 and H18N11, have been identified in bats.)
Many different combinations of HA and NA proteins are possible. (18x11=198
combinations)
For example, an "A(H7N2) virus" designates an influenza A virus subtype that has an
HA 7 protein and an NA 2 protein. Similarly, an "A(H5N1)" virus has an HA 5 protein
and an NA 1 protein.
antigenic drift
Flu virus surface proteins (HA and NA) can change in two ways. Antigenic drift and shift.
Flu viruses change all the time due to antigenic drift, but antigenic shift happens less
frequently
Antigenic Assortment
Viral segmented genome reassortment in mixed infections
256 genetically assorted progeny viruses
Genetic reassortment between human and avian viruses
Global cycle of avian influenza in animals
Reassortment
, (antigenic shift; how pandemic viruses are born)
Schematic presentation of putative "mixing vessel" host species
Schematic presentation of putative "mixing vessel" host species (pigs, quails, turkeys,
humans) which express sialic acid receptors for both avian- and human adapted
influenza A viruses (IAV) in their respiratory tracts. Hence, they are considered
susceptible for a wider range of IAV of different host origins. Co-infections with different
IAV create reassortment opportunities increasing the likelihood of the formation of
reassortants with increased zoonotic or pre-pandemic propensity
Disease in Poultry (LP and HP)
Low Pathogenic
-Subclinical infection
-Primarily respiratory
-Decreased egg production
Highly pathogenic
-100% mortality rate within 24 hours of exposure (no time for clinical signs to develop)
Clinical signs of influenza
Incubation period: 3-14 days
Birds found dead
Drop in egg production
Neurological signs
- Depression, anorexia, ruffled feathers
Combs swollen, cyanotic
Conjunctivitis and respiratory signs
