Download Respiratory Diseases

Amman
May, 5, 2009
Influenza A Viruses
Mohammad Q Al-Natour, DVM, MPH, Ph.D
Associate Prof. of Avian Diseases
[email protected] & [email protected]
Mobile: 0795-134-993
Avian Diseases Research Lab.
Department of Pathology & Animal Health
Faculty of Veterinary Medicine
Jordan University of Science and Technology
Irbid - Jordan
Key properties of type A
influenza virus
Multiple serotypes
 Wide spectrum of pathogenicity
 Wide host range
 Global ?
 International trade & of economic
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significance??
Incubation period (H1N1): 1-3 days in pigs
Pigs excreting virus within 24 hrs of infection
Virus shedding for 7-10 days
Pigs recover within 5-7 days
Orthomyxoviridae
Humans
Horses
Influenza virus A
Cats
Pigs
Birds
Marine mammals
Influenza virus B
Influenza virus C
Humans
Pigs
Humans
Orthomyxoviridae
A.I. Virus
Single stranded RNA –ve
 Segmented: 8 genes cod for 10 proteins
 Two glycoprotein surface projection:
- Haemagglutinin (HA): H1-H16
- Neuraminidase (NA): N1-N9
 Enveloped (20% lipid): Sensitive to heat, dryness and
normal disinfectants
 Antigenic types A, B, C
 Pathogenicity vary

Haemagglutinin and Neuraminidase
sialic acid
on receptor
HA
receptor
binding
site
variable
loops
N
active site
variable
loops
Cleavage of HA
binds
receptor
HA0
penetrates
cell
Clara (mucus),
extracellular,
serum,
bacterial
proteases
binds
receptor
HA1
HA2
HA cleavage and virulence
May ‘94 ->
June ‘94
PQ--RETR
Dec ‘94 -> P Q R K R K T R
Jan ‘95
low
cleavability
low
virulence
respiratory
infection
high
cleavability
high
virulence
systemic
infecton
?
Influenza virus replication
HA cleaved
by
proteases
HA binds to
receptor
virus
buds
lowered
pH, HA
fuses
membranes
virus in
phagolysosome
RNA
released
N releases
virus
Infection cycle of influenza
1.
2.
3.
4.
5.
6.
7.
Binding of virus to cell
Cell engulfs virus via
endocytosis
Membrane of virus fuses with
endosome; RNA released into
cell
Viral polymerase produces
mRNA from viral RNA
Protein, new RNA produced
Self-assembly produces virions
Virions bud off cell membrane
Infection cycle:
Binding and endocytosis

HA contains receptor binding
site for virus
– Binds to sialic acid residue on
cell surface glycoprotein

Binding triggers receptormediated endocytosis
– Virus is taken into endosome
– Low pH of endosome causes
fusion of viral and endosome
membranes
Type A Influenza Surface Antigens
Surface Antigen Subtype
Hemagglutinin:
1 2 3
Human   
Equine

Swine 

Avian   
Neuraminidase:
1 2 3
Human  
Equine
Swine  
Avian   
4 5 6 7 8 9 10 11 12 13 14 15 16

           
4 5 6 7 8 9
 
     
Reassortment
Evolution and Spread of flu viruses
pigs
poultry
aquatic birds
fecal/oral
All HA and N
serotypes
H1N1
H3N2
H1N1
humans H2N2
H3N2
(H5N1, H9N2)
horses H3N8
H7N7
respiratory
The avian HK viruses
Swayne, D.E. Epidemiology of Avian Influenza in Agricultural and Other
Man-Made Systems. In: Avian Influenza. Wylie-Blackwell, in press,
March, 2008.
Swayne, D.E. Understanding the ecology and epidemiology of avian
influenza viruses: implications for zoonotic potential. In: Emerging
Infectious Diseases of Animals. pp. 101-130, ASM Press, 2000.
Generation of Pandemic Influenza Strain
Avian
virus
Avian
reassortant
virus
Avian
virus
Human
virus
Reassortment
in swine
CDC
Reassortment
in humans
Avian-human
pandemic
reassortant
virus
19
Influenza A(H1N1) - update
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4 May 2009 -- As of 06:00 GMT, 4 May 2009, 20 countries have
officially reported 985 cases of influenza A (H1N1) infection.
Mexico has reported 590 laboratory confirmed human cases of
infection, including 25 deaths. The higher number of cases from
Mexico reflects ongoing testing of previously collected specimens. The
United States has reported 226 laboratory confirmed human cases,
including one death.
The following countries have reported laboratory
confirmed cases with no deaths - Austria (1), Canada (85),
China, Hong Kong Special Administrative Region (1),
Costa Rica (1), Colombia (1), Denmark (1), El Salvador
(2), France (2), Germany (8), Ireland (1), Israel (3), Italy
(1), Netherlands (1), New Zealand (4), Republic of Korea
(1), Spain (40), Switzerland (1) and the United Kingdom
(15).
Influenza A(H1N1) - update

There is no risk of infection from this virus
from consumption of well-cooked pork and
pork products.
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It is considered prudent for people who are ill to delay
international travel and for people developing symptoms
following international travel to seek medical attention, in
line with guidance from national authorities. Individuals
are advised to wash hands thoroughly with soap and water
on a regular basis and should seek medical attention if they
develop any symptoms of influenza-like illness.
WHO advises no restriction of regular travel or closure of
borders.
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The A/H1N1 situation needs to be
carefully monitored.
Influenza viruses, whether in humans or
among animals, are constantly evolving
genetically, along with changes in their
ability to cause morbidity and mortality in
humans or animals. Therefore the current
A/H1N1 situation should be carefully
monitored as many of the virus
characteristics and developments are still
unknown, Domenech said.
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Surveillance for porcine respiratory disease should be
intensified and all cases of porcine respiratory syndrome
are recommended to be immediately reported to veterinary
authorities. It is also recommended to inform OIE and
FAO about any occurrence of outbreaks of the new
A/H1N1 Influenza virus in pigs.
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Strict biosecurity measures including restriction of
movements of pigs, goods and people should be applied on
all farms or holdings with swine showing signs of clinical
respiratory illness until diagnosis of the illness has been
made.
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Where A/H1N1 influenza is confirmed, movement restrictions should
be in force for seven days after the last animal has recovered.
Governments are requested to provide full support in improving
biosecurity measures particularly to small and medium pig farmers.

Persons who work directly with swine should be urged not to go to
work if they have any signs of respiratory disease, fever or any
influenza-like illness. Animal handlers and veterinarians should wear
protective clothing to minimize the risk of being infected.
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FAO stressed that there is absolutely no need to slaughter animals in
view of preventing circulation of the A/H1N1 virus.
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The agency emphasized that the A/H1N1 virus cannot be transmitted
to humans by pork and pork products. Pork and pork products, handled
in accordance with good hygienic practices recommended by the
FAO/WHO Codex Alimentarius Commission and the OIE, will not be
a source of infection.
Thank You

Avian Flu in Arabic
Language


Prof. Abo-Shehada
Dr. Al-Natour

2nd Edition, 2007
M. N. Abo-Shehada
M. Q. Al-Natour
2007