Transcript Information about AVIAN Influenza

Information about AVIAN
Influenza
Harvey Kayman, MD, MPH, PHMO III
California Department of Public Health
Division of Communicable Disease Control
Immunization Branch
Objectives
• Learn about Global Avian
Influenza
• Learn what challenges we face
• Learn how to prevent, protect,
and mitigate
Why is there such concern now?
• Health professionals are
concerned that the continued and
expanded spread of a highly
pathogenic AVIAN H5N1 virus
across eastern Asia and other
countries represents a significant
threat .
Challenge
• The current outbreaks of highly pathogenic
avian influenza, which began in SouthEast Asia in mid-2003, are the largest and
most severe on record.
• Never before in the history of this disease
have so many countries been
simultaneously affected, resulting in the
loss of so many birds.
Influenza A viruses have 16 H subtypes
and 9 N subtypes.
• In poultry, the viruses can mutate, usually within
a few months, from then low pathogenic avian
influenza (LPAI) form into the highly pathogenic
form (HPAI).
• Only viruses of the H5 and H7 subtypes are
known to cause the highly pathogenic (HPAI)
form of the disease.
Influenza A HA and NA Subtypes
H1
H2
H3
H4
H5
H6
H7
H8
H9
H10
H11
H12
H13
H14
H15, H16
N1
N2
N3
N4
N5
N6
N7
N8
N9
Highly Pathogenic Avian Influenza
HPAI
• In 2004, over 120 million birds died or
were destroyed as a result of a
current avian influenza type, the
H5N1 strain. This number is higher
than the combined total bird deaths of
all prior highly pathogenic outbreaks
recorded throughout the world over
the last four decades.
Changing viral behavior in natural
reservoir, wild waterfowl,
• The spring 2005 die-off of upwards of 6,000
migratory birds at a nature reserve in central
China, caused by highly pathogenic H5N1, was
highly unusual and probably unprecedented.
• In the past, only two large die-offs in migratory
birds, caused by highly pathogenic viruses, are
known to have occurred: in South Africa in 1961
(H5N3) and in Hong Kong in the winter of 2002–
2003 (H5N1).
Acceleration of HPAI
• Furthermore, the 2004 deaths
occurred in just three months.
• In the subsequent months, H5N1 has
expanded to include other wild birds
as well as domesticated ducks, and
• its host range now also includes
mammals.
More lethal in more animals
• When compared with H5N1 viruses
from 1997 and early 2004, H5N1
viruses now circulating are more
lethal to experimentally infected mice
and to ferrets (a mammalian model)
and survive longer in the
environment.
The AVIAN H5N1 virus has raised
concerns about a potential human
pandemic because:
• It is especially virulent.
• It is being spread by transported
domestic poultry.
• It can be transmitted from birds to
mammals and in some limited
circumstances to humans.
A growing number of human H5N1
cases have been reported
• in Azerbaijan, Cambodia, China, Egypt,
Indonesia, Iraq, Thailand, Turkey and Vietnam.
• More than half of the people infected with the
H5N1 virus have died.
• Most of these cases are believed to have been
caused by exposure to infected poultry.
• The concern is that H5N1 will evolve into a virus
capable of human-to-human transmission.
H7N# Disease Risks
• An H7N2 virus strain isolated in 2003.
• This North American avian influenza A--H7 virus
is partially adapted to recognize human upper
respiratory tract sugar receptors.
• Alpha 2-6 receptors are found in humans
• Alpha 2-3 receptors are found in the guts of wild
birds (their natural host) and domestic poultry.
Those receptors are scarce in the human upper
respiratory tract. CDC's Division of Media Relations (6/10/08)-http://www.cdc.gov/flu/avian/
H7N# Disease Risks
• H7N7 outbreak in the Netherlands in 2003
• H7N3 viruses responsible for British
Columbia's massive poultry outbreak in
2004
• > 17 million chickens destroyed to stop
2004 outbreak.
• Need to develop vaccines for H7, as well
as H5N1
Dr. Ron Fouchier, with the Erasmus Medical Centre in Rotterdam, the Netherlands. (5/08)
Human-Poultry interaction
• Poultry being carried on the Siliguri-Darjeeling
highway, that harbored the H5N1 virus, helped it
to spread to a region where 4,000,000 poultry
had previously been culled in West Bengal to
decrease risk of Avian influenza.
• Sources said that the Panchayat elections in
West Bengal had severely affected the state's
bird flu control and containment operations.
• State officials in 4 districts did not want to
intimidate villagers by taking away their birds.
• This, they said, could cost their vote during
upcoming elections. May 11, 2008 The Times of India Group
Time to prepare
• While no one can state with
complete certainty that a
pandemic will occur, the signs
point to it being a prudent time to
begin careful and thorough
preparation.
Low Pathogenic Avian Influenza LPAI
• H5 and H7 viruses are introduced to
poultry flocks in their low pathogenic form
(LPAI).
• The so-called “low pathogenic” form
commonly causes only mild symptoms
(ruffled feathers, a drop in egg production)
and may easily go undetected.
HPAI
• First identified in Italy in 1878
• HPAI causes severe disease, rapid
contagion and lethal for > 6 of 8 chickens
inoculated with the virus.
• It spreads very rapidly through poultry
flocks, causes disease affecting multiple
internal organs, and
• Has a mortality that can approach 100%,
often within 48 hours.
HPAI Environmental Survival
• Highly pathogenic viruses can survive for
long periods in the environment, especially
when temperatures are low.
• For example, the highly pathogenic H5N1
virus can survive in bird feces for at least
35 days at low temperature (4°C).
• At a much higher temperature (37°C),
H5N1 viruses have been shown to survive,
in fecal samples, for six days.
The role of migratory birds in the
spread of HPAI
• The role of migratory birds is not fully
understood.
• Wild waterfowl are considered the natural
reservoir of all influenza A viruses.
• They have probably carried H5 and H7
subtypes of LPAI, with no apparent harm,
for centuries.
In the past, HPAI was rare in
Migratory Birds
• In the past, only a few migratory birds
were found dead within the flight
range of a poultry outbreak.
• Current concept is that wild waterfowl
are not agents for the onward
transmission of HPAI.
The role of Ducks in the spread
of HPAI
• Domestic ducks excrete large quantities
of highly pathogenic virus without
showing signs of illness.
• Mallards act as a “silent” reservoir of the
virus, perpetuating transmission to other
birds.
• Adding another layer of complexity to
control efforts and removes the warning
signal for humans to avoid risky
behaviors.
HPAI Transmission
• Migratory birds can introduce LPAI H5 and H7
viruses to poultry flocks, which then mutate to
HPAI.
• Avian influenza viruses are readily transmitted
from farm to farm by the movement of live birds,
• People (especially when shoes and other
clothing are contaminated), and
• Contaminated vehicles, equipment, feed, and
cages.
Human controlled intensive ricedomestic duck agriculture
• Virus persistence after extensive culling is
increasingly confined to areas in eastern
and southeastern Asia where humans
cultivate rice and duck meat.
• ~90% of the world’s 1.044 billion domestic
ducks are in Asia.
• China and Viet Nam=775 million or 75%.
• Thailand=11 million ducks.
•
http://www.fao.org/newsroom/en/news/2008/1000817/index.html
Dead birds don't fly
• Governments should stop blaming wild
birds for outbreaks of the disease.
• Migratory birds do not move during the
summer, (Ornithologist Martin Williams)
• Waterfowl carry a lot of bird flu viruses, but
they don't carry the Highly Pathogenic
Avian H5N1 flu, because it kills them.
•
June 2008 South China Morning Post Publishers Limited, Hong Kong.
Backyard flocks=a heightened risk
of human exposure and infection.
• Backyard flocks usually roam freely.
• Backyard flocks scavenge for food
• Backyard flocks mingle with wild birds or
share water sources with them.
• Abundant opportunities for human
exposure to the virus with birds in
households, especially during adverse
weather, or when they share areas where
children play or sleep.
Endemic Zoonotic H5N1 virus -especially tenacious.
• Despite the death or destruction of an
estimated 150 million birds, the virus is
now considered endemic in many parts of
Indonesia and Viet Nam and in some parts
of Cambodia, China, Thailand, and
possibly also the Lao People’s Democratic
Republic.
• Control of the disease in poultry is
expected to take several years.
Disease outbreak maps June 2008
Ducks, rice and people
• A strong link between duck grazing patterns and
rice cropping intensity in H5N1 highly
pathogenic avian influenza in Thailand and Viet
Nam.
• Ducks feed mainly on leftover rice grains in
harvested paddy fields, so free-ranging ducks in
both countries are moved to many different sites
in line with rice harvest patterns.
• Virus persistence is now increasingly confined to
areas with intensive rice-duck agriculture in
eastern and southeastern Asia.
•
"Mapping H5N1 highly pathogenic avian influenza risk in Southeast Asia: ducks, rice and people", Proceedings of
the National Academy of Sciences of the United States (PNAS),
http://www.fao.org/newsroom/en/news/2008/1000817/index.html
90 % of the world’s 1.044 billion
domestic ducks are in Asia
• China and Viet Nam account for the bulk
of this – 775 million or 75 percent.
Thailand has about 11 million ducks.
Control of HPAI in Thailand
• The local movements of ducks decreased
when the Thai government started to
support in-door keeping of ducks, offering
feed subsidies and construction of
enclosures.
• Together, these measures stopped the
H5N1 transmission cycle and since late
2005 Thailand has suffered only sporadic
outbreaks.
Control of HPAI in Vietnam
• Viet Nam started nationwide vaccination of
all poultry at the end of 2005, including the
Mekong delta which is home to 50 million
ducks.
• This large-scale vaccination was repeated
in 2006/07.
• Initially, human infections disappeared and
levels of disease in poultry fell noticeably.
• Only gradually did H5N1 viruses reappear, mostly in unvaccinated ducks and
particularly in the Mekong delta.
How avian influenza A/H5N1 might
enter the U.S. bird population
• Poultry imported into South America (where
poultry trade is less restricted) from countries
where H5N1 has affected domestic or wild
birds poses the greatest risk of introducing
H5N1 into the U.S.
• H5N1 could be transmitted from poultry in
South America to birds that migrate to North
America*
*Kilpatrick et al. Proc Natl Acad Sci. 2006 Dec 19;103(51):19368-73
By 2004, expanded to other
mammalians. Now found in:
•
•
•
•
•
•
Tigers,
Leopards,
Pigs,
Domestic cats,
Palm civets,
Humans
World wide Human Mortality
Rate=63%
June 2008
400
350
300
250
Cases
Deaths
Rate
200
150
100
50
0
Mortality
Indonesia
Vietnam
Thailand
Protective and Mitigating
responses
• Governmental preparedness
• Cross Sector planning and collaboration
• Cross Boundary planning and
collaboration
• Expansion of Surveillance, Case tracking
and Epidemiology
• Laboratory Diagnostic Enhancement
• Improved information systems
WHO guidance on public health measures in
countries experiencing their first outbreaks of
H5N1 avian influenza-October 2005
• Coordination of services. Multi-sectoral
procedures should be put in place to
coordinate the work of agricultural,
veterinary and public health services (and
any other sectors deemed appropriate in a
country context) and facilitate the
exchange of laboratory and
epidemiological data.
•
http://www.who.int/csr/disease/avian_influenza/guidelines/firstoutbreak/en/index.html
Control Measures
• Rapid culling of all infected or exposed
birds,
• proper disposal of carcasses,
• the quarantining and rigorous disinfection
of farms, and
• the implementation of strict sanitary, or
“bio-security”, measures
Control Measures
• Restrictions on the movement of live
poultry, both within and between countries,
• The logistics of recommended control
measures are most straightforward when
applied to large commercial farms, where
birds are housed indoors, usually under
strictly controlled sanitary conditions, in
large numbers.
http://www.who.int/mediacentre/factsheets/avian_influenza/en/index.html
Control Measures
• Control is far more difficult under
poultry production systems in which
most birds are raised in small
backyard flocks scattered throughout
rural or peri-urban areas.
• http://www.who.int/mediacentre/factsheets/avian_influenza/en/index.
html
Vaccination for public health
purposes.
• At least some pandemic viruses are
known to have emerged following a reassortment event.
• Vaccination against seasonal influenza will
not protect people against infection with
the H5N1 virus; no vaccine against H5N1
is presently available.
Potential sources of exposure
• Swimming in water bodies with discarded
infected carcasses or contaminated by infected
ducks feces.
• No known plausible exposure source,
suggesting an unknown environmental factor,
involving contamination with the virus.
• A possible role of peri-domestic birds, such as
pigeons
• The use of untreated bird feces as fertilizer.
Poverty exacerbates the problem
• In situations where a prime source of food
and income cannot be wasted, households
frequently consume poultry when deaths
or signs of illness appear in flocks.
• This practice carries a high risk of
exposure to the virus during slaughtering,
de-feathering, butchering, and preparation
of poultry meat for cooking, but has proved
difficult to change.
Smoldering Rural Outbreaks
• Owners may not interpret deaths or signs
of illness in a flock as a signal of avian
influenza and a reason to alert the
authorities.
• The absence of compensation to farmers
for destroyed birds works against the
spontaneous reporting of outbreaks
• Encourages owners to hide their birds
during culling operations.
Protection of persons at risk of
occupational exposure
• Personal protective equipment. Those at risk
of occupational exposure on affected or at-risk
farms should wear personal protective
equipment:
• 1. Protective clothing, preferably coveralls plus
an impermeable apron or surgical gowns with
long cuffed sleeves plus an impermeable apron;
2. Heavy-duty rubber work gloves that may be
disinfected;
Personal protective equipment
• 3. Standard well-fitted surgical masks should be
used if high-efficiency N95 respiratory masks
(NIOSH-certified N-95 or equivalent) are not
available. Masks should be fit-tested and
training in their use should be provided;
4. Goggles;
5. Rubber or polyurethane boots that can be
disinfected or protective foot covers that can be
discarded.
Pharmaceutical prophylaxis and
treatment.
• Those at risk of occupational
exposure on affected or at-risk farms
can be protected via antiviral
prophylaxis (oseltamivir) or postexposure prophylaxis.
• Antivirals should be readily available
for the treatment of suspected and
confirmed cases.
http://www.who.int/csr/disease/avian_influenza/en/
WHO Recommendations
• WHO continues to recommend that travelers to
affected areas should avoid contact with live
animal markets and poultry farms, and any freeranging or caged poultry.
• Large amounts of the virus are known to be
excreted in the droppings from infected birds.
• Populations in affected countries are advised to
avoid contact with dead migratory birds or wild
birds showing signs of disease.
http://www.who.int/csr/disease/avian_influenza/en
Exposure Risk
• Direct contact with infected poultry, or surfaces
and objects contaminated by their droppings, is
considered the main route of human infection.
• Exposure risk is considered highest during
slaughter, de-feathering, butchering, and
preparation of poultry for cooking.
• There is no evidence that properly cooked
poultry or poultry products can be a source of
infection.
Poultry Consumption or Traveling
to an Affected Country
• Not a risk factor, provided poultry is thoroughly
cooked and the person is not involved in food
preparation.
• Traveling to a country with outbreaks in poultry
or sporadic human cases does not place a
traveler at enhanced risk of infection.
• Currently, no efficient human-to-human
transmission of the virus.
• Avoid visiting live or “wet” poultry markets,
farms, or other environments where exposure to
diseased birds may occur.
Health monitoring.
Those at risk of occupational
exposure should:
• 1. Be aware of the early clinical signs of H5N1
infection, but also understand that many other
common diseases – of far less health concern –
will show similar early symptoms.
• 2. Check for these signs (especially fever) each
day during potential exposure and for 14 days
after last exposure.
• 3. Communicate any symptoms to a designated
local physician and provide background
information on exposure history.
Symptoms
• Most patients infected with the H5N1 virus show
initial symptoms of fever (38 C or higher)
followed by influenza-like respiratory symptoms,
including cough, rhinorrhea, sore throat, and
(less frequently) shortness of breath.
• Watery diarrhea is often present in the early
stages of illness, and may precede respiratory
symptoms by up to one week.
• Gastrointestinal symptoms (abdominal pain,
vomiting) may occur and headache has also
been reported.
Challenges
• Disposal
• Occupational health
• Developing new wild
bird surveillance
program
• Hunting?
• Public perception –
panic?
General Resources
• Links to Additional Information
• http://www.pandemicflu.gov/ (managed by
the Department of Health and Human
Services)
• http://www.cdc.gov/flu/avian/ (managed by
the Centers for Disease Control and
Prevention)
WHO Resources
• http://www.who.int/csr/disease/avian_influ
enza/avian_faqs/en/index.html#howdoes
• http://www.who.int/csr/resources/publicatio
ns/influenza/WHO_CDS_CSR_GIP_05_8EN.pdf
The STATE BIRD HOTLINE:
866–922–BIRD (2473)
• http://www.cdfa.ca.gov/ahfss/Emergency_
Projects_Support/Bird_Hotline.html
• People can call this number to quickly
report sick or dead poultry, wild birds,
or pet birds.
• The public can obtain information on
how to know when their birds are sick,
and how to protect their birds from
disease.