Transcript Avian Influenza - Salvador Abad

AVIAN INFLUENZA
Influenza: A devastating
disease!
“Flu spreads across the world and
412 BC: Epidemic reported by
ages.”
Hippocrates
1580: First pandemic
1781 & 1830: Epidemics Asia -> Russia
1918: Spanish Flu killed 20-40M
people
1933: First human influenza virus
isolated
1957: Asian Flu
1968: HongKong Flu
1977: Russian Flu
Influenza:
 “The World Health Organization
(WHO) estimates that seasonal
influenza epidemics result in 3 to 5
million cases of severe illness and
lead to 250,000 to 500,000 deaths
each year worldwide.”
 “Influenza affects all ages.”
DOH - Technical Working Group on Influenza, Nov. 20, 2003
TEN LEADING CAUSES OF MORBIDITY
(No. & Rate/100,000 Population)
PHILIPPINES, 2001
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CAUSE
1. Diarrheas
2. Bronchitis/Bronchiolitis
3. Pneumonias
4. Influenza
5. Hypertension
6. TB Respiratory
7. Diseases of the Heart
8. Malaria
9. Measles
10. Chickenpox
NO.
845.526
694,836
652,585
499,887
318,521
110,841
47,040 60.4
40,543 52.0
24,494 31.4
24,359 31.3
RATE
1085.0
891.7
837.4
641.5
408.7
142.2
INFLUENZA: BY AGE GROUP
(No. & Rate/100,000 Population)
PHILIPPINES, 2001
160,000
140,000
120,000
100,000
80,000
60,000
40,000
20,000
0
<1 yr
1-4 yrs. 5-14 yrs. 15-49 yrs.50-64 yrs. >65 yrs.
Female
Male
Classification
RNA virus
Family:
Genus:
Types:
Specificity:
ORTHOMYXOVIRIDAE
Influenza virus
Influenza C virus
Type A
Type B
Type C
Man
Animal
Man
Man
Kingsbury D. W., Virology, IInd edition, New York, 1990, 1076-87
Structure: segmented and
enveloped viruses
Nucleocapsid:
Nucleoprotein (NP) -RNA (7 or 8 segments)
Internal
antigens
Matrix protein (M)
Lipid bilayer
Haemaglutinin (HA)
Neuraminidase (NA)
Surface
antigens
80 to 120 nm
Kingsbury D. W., Virology, IInd edition, New York, 1990, 1076-87
Antigenic drift
 Affects Influenza A and B viruses
 Occurs every year or every few years
within an influenza subtype
 Mutations affecting RNA amino acids
 Does not result in new subtype
 Can result in significant epidemics
Antigenic shift:
emergence of a "new" virus worldwide
 affects only Influenza A virus
 major and sudden genetic
variations in HA and/or NA
 no immunity in population
 intervals between
previous
pandemics - 11 to 42 years
 last pandemic in 1968/69
What is Bird Flu?
An infectious disease of birds ranging from
mild to severe form of illness.
All birds susceptible to avian influenza,
though some species are more resistant to
infection than others.
Some forms of bird flu infections can
cause illness to humans.
What causes bird flu?
Bird flu is caused by15 subtypes of
influenza A virus subtype of avian
influenza .
Viruses of low pathogenicity can, after
circulation for sometimes short periods in a
poultry population, mutate into highly
pathogenic viruses.
Host distribution of influenza A
subtypes
HA subtypes
Man
Swine
Horse
Seal
Turkey
Duck
NA subtypes
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H1 H2 H3 H4 H5 H6 H7 H8 H9 H10
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H15
N1 N2 N3 N4 N5 N6 N7 N8 N9
+
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To date, all outbreaks of the highly pathogenic
form have been caused by influenza A viruses
of subtypes H5.
Kilbourne E. D., Influenza, New York, plenum 1987:229-51
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Avian Flu in 1997
A/ QUAIL/HONG KONG /G1/97 VIRUS
 1997 – H5N1 – Hongkong, 18
human cases, 6 died (30%
mortality)
 Birds - actual source of human
infection
 No person –to- person transmission.
 This occurrence highlighted the
potential of new and lethal pathogens
to emerge unexpectedly.
Recent cases of human infection
caused by avian influenza viruses
(New Influenza Virus Subtypes)
1997 - H5N1 - Hongkong, 18 cases, 6 human deaths
1999 – H9N2 - Hongkong, I human case, mild infection
2003 – H5N1 – Hongkong – 2 human cases, 1 death
H7N7 – The Netherlands, hundreds with
conjunctivitis, ILI , 86 confirmed,
3 cases w/ human-to-human
transmission, 1 human death (a
veterinarian)
H9N2 – Hongkong – 1 human case, mild infection
H5N1 - South Korea, Japan – death of chickens,
no human case
2004 - H5N1 - human cases and death in Vietnam and
Thailand.
How is bird flu transmitted to
chickens and other birds?
 Direct contact with discharges from
infected birds, especially feces and
respiratory secretions
 Contaminated feed, water, cages
equipment, vehicles and clothing
 Clinically normal waterfowl and sea birds
my introduce the virus into flocks
 Broken contaminated eggs may infect
chicks in the incubator
How is bird flu transmitted in
chickens and other birds?
 Birds that survive infection excrete
virus for at least 10 days, orally and
in feces
 Highly pathogenic viruses can
survive for long periods in tissues,
water and the environment,
especially when temperatures are
low.
How is bird flu transmitted to
humans?

Direct or indirect contact with infected wild ducks
and chickens through infected aerosols,
discharges and surfaces.

Based on present knowledge, there appears to be
no risk of transmission of the H5N1 virus to
humans from raw, chilled or frozen poultry foods.

Since the virus is easily inactivated by heat, one
does not get bird flu from thoroughly cooked
chicken meat.
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No evidence of human-to- human transmission.
Why are we concerned with
bird flu?

With its capacity to cause severe disease
(high pathogenicity ) and epidemics, it
causes severe epidemics and mass death of
chickens
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The poultry industry and food security feared
to be greatly affected

High mortality to humans
Why are we concerned with
bird flu?

Influenza A viruses have the capacity and
propensity to mutate and recombine with
another subtype of influenza virus in humans
resulting into a totally new influenza A virus
subtype.

This new subtype having the characteristic of
human influenza virus of being capable to
spread from one person to another.

The absence of immunity to the totally new
virus through previous infection and no
existing vaccines can confer protection make
the human population vulnerable, leading to
high number of cases and deaths worldwide
(pandemic).
Hypothesis concerning pandemics
occurence
 Direct transfer of
viruses between
animals and humans
 New subtypes are
reassortants of
human and
waterfowl Influenza
virus
 Pig or humans "mixing vessel" of
human and avian
influenza virus
Wild
aquatic birds
Humans
Human
or
Swine
South China: Pandemics
starting-point?
Kawaoka Y., Bean W. J., Gorman O.T., et al. In : Elsevier Science Publishers B.V.
1992: 187-91
Scholtissek C, Shultz U, Ludwig S, Fitch WM. In : Elsevier Science Publishers B.V.
1992: 193-201
Subtype emergence and recirculation
20th century pandemics
Year
Designation
191 "Spanish flu" H1N1
"Asian flu" H2N2
8
195 "Hong Kong flu" H3N2
"Russian flu" H1N1
7
196
8
197
7
Extent of antigenic change in
indicated surface protein
Severity of
pandemic
HA/NA: major change
HA/NA: major change
HA: moderate change
recirculation
Severe
Severe
Moderate
Mild
Betts FR, Douglas RG, Mandell G.L., Douglas R. G., Bennett J.E., Principles and practice of infectious diseases, 3rd ed., 1990;39:1306-25
What are the signs of bird flu in
chickens?
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Sudden onset, severe illness
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Severe depression, inappetence
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Drastic decline in egg production
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Facial edema with swollen and cyanotic combs and
wattles
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Petechial hemorrhages on internal membrane
surfaces
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Sudden deaths (mortality that can reach 100%)
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Virus isolation needed for definitive diagnosis
What are the signs and symptoms
of bird flu in humans?

A (H5N1) infection very similar to other
influenza viruses, most will be self-limiting

Initial symptoms are fever, malaise, myalgia,
sore throat and cough.
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Conjunctivitis in some patients
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Persistently high fever
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X-ray of the chest is useful in detecting early
viral pneumonia.
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Complications and death due to severe
pneumonia, respiratory distress syndrome
and multi-organ failure.
8. Since there are so many cases of influenza,
pneumonia or any other respiratory illness, when
does one suspect that the patient is a case of bird flu?
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If the patient has had direct or indirect
contact through handling or having taken
care or getting near sick chickens or other
birds.
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A laboratory confirmation of the bird flu
infection and epidemiologic link with
unusual death or epidemics of chickens will
support the diagnosis of bird flu.
What is the treatment of bird
flu?
 One should not wait for the laboratory
diagnosis of H5N1, infection before
treatment is started.
 Treatment for HSN, infection is
essentially the same as for other
influenza viruses.
 Antiviral drugs for both treatment and
prevention, but have some limitations.
How do we prevent bird flu?
 The ban on importation of live
chickens and other poultry products
from countries affected with bird flu
is a critical step to prevent the entry
of bird flu into the country.
How do we prevent bird flu?
For poultry caretakers and handlers of
chickens and other birds:

Avoid contact of poultry with wild birds, in particular
waterfowl
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Do not import/ avoid introduction of birds of unknown
health condition into flock
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Control human traffic into poultries
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Practice proper hand washing and cleaning and
disinfection procedures in poultries
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Report to authorities any unusual death or illness of
chickens and other birds
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Report to authorities any illness among the workers in
poultry farms
How do we prevent bird flu?
For consumers and the general public:

Thoroughly wash hands with soap and water before and
after handling chicken meat
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Clean kitchen surfaces and utensils before and after use

Cook chicken well by seeing to it that the boiling
temperature is reached
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Go only to places where there are no wild waterfowl
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Report to authorities any unusual death or illness of
chickens and other birds

Report to authorities any case of respiratory illness with
history of exposure to sick or dead chickens and other
birds
How do we prevent bird flu?
♦ Everyone should consider getting a vaccine for influenza.
Priority should be given to those who are directly exposed
to birds.
Is it safe to travel to countries
affected with bird flu?
 Bird flu is not transmitted from one person
to another.
 Individuals at risk are those who are
directly or indirectly exposed to sick
chickens and other fowl.
 The government thereby advises travelers
to countries affected with bird flu not to go
to bird parks (aviaries) and poultry farms.
Summary
Avian influenza viruses can infect and have infected people
through close, unprotected direct contact with infected
poultry.
Human infection with high path avian influenza viruses has
resulted in mild to severe illness.
There is no current evidence of sustained person to person
transmission.
However, these viruses are continuing to evolve and have
the potential for genetic resentment to evolve into a virus
that may be more easily transmissible among humans which
can result to a pandemic .