Transcript 禽類流行性感冒﹙ Avian Influenza﹔Bird Flu ﹚

禽類流行性感冒
﹙ Avian Influenza; Bird Flu ﹚
中國醫藥大學附設醫院
實習醫生︰高 敏 欽
March 2, 2k4
於台中市立大業國中
Three Types of Influenza Viruses
 Influenza A, B, and C.
 Each year about 20,000 Americans die because of
influenza or influenza related pneumonia. Over
90% of the deaths occur in persons aged 65 years
and older.
 The current subtypes of influenza A viruses found
in people are A(H1N1) and A(H3N2).
 Influenza A(H1N1), A(H3N2), and influenza B
strains are included in each year's influenza
vaccine.
 The flu shot does not protect
against type C influenza.
Introduction Influenza A virus
 Infect various animal hosts (avian, mammalian).
 Serologic and genetic analysis:
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15 hemagglutinin (HA)
 9 neuraminidase (NA)
 Only 3 of the 15 HA subtype have caused
pandemics in human
 H1N1 in 1918 (Spanish, swine), 20 million deaths,
Avian ancestor.
 H2N2 in 1957 (Asian), 86,000 deaths (U.S.), avian
reassortment.
 H3N2 in 1968 (HK), 34,000 deaths (U.S.), avian
reassortment.
 H1N1 reemerge in 1977 (Russian), negligible.
Background on Pandemics
 1918-19, "Spanish flu," [A (H1N1)], caused
the highest number of known flu deaths:
more than 500,000 people died in the
United States, and 20 million to 50 million
people may have died worldwide. Many
people died within the first few days after
infection and others died of complications
soon after. Nearly half of those who died
were young, healthy adults.
Background on Pandemics (cont.)
 1957-58, "Asian flu," [A (H2N2)], caused
about 70,000 deaths in the United States.
First identified in China in late February
1957, the Asian flu spread to the United
States by June 1957.
 1968-69, "Hong Kong flu," [A (H3N2)],
caused approximately 34,000 deaths in
the United States. This virus was first
detected in Hong Kong in early 1968 and
spread to the United States later that year.
Type A (H3N2) viruses still circulate today.
Morphology of Influenza A virions
 Orthomyxoviridae
 spherical and 80-
200nm in diameter
 8 segments of （-）
ssRNA
 "spikes" of
haemagglutinin (HA)
and neuraminidase
(NA)
Influenza A polypeptides
Segment Size (nt) Polypeptide
Function
1
2341
PB2
2
2341
PB1
3
2233
PA
4
1778
HA
Subunit of polymerase, active
synthesis
Haemagglutinin
5
1565
NP
Nucleoprotein: Part of transcriptase complex
6
1413
NA
Neuraminidase: release of virus
7
1027
M1
Matrix protein: Major component of virion
M2
Integral membrane protein: Ion channel
NS1
Anti-interferon protein. Effects on cellular RNA
transport
RNP nuclear export
8
890
NS2
Subunit of polymerase: Host cap binding and
endonuclease
Catalytic subunit of polymerase
in vRNA
The Life Cycle of Influenza Virus
Inactivation of Influenza A virus
 Radiation
 pH>9 or <5
 Temp. above 50°C (56°C, 3h; 60°C, 30m)
 Detergents and organic solvents
 Drying in 24~48 h
 在糞便中的病毒，0℃下可存活三十天，
20℃下僅存活七天。
Characteristics of Influenza
 mortality: 0.01%
 flu spread: droplet
spread.
 flu season: from late
December through
March.
Clinical Signs and Symptoms
of Influenza
 Fever, nonproductive cough, myalgia,
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headache, severe malaise, pharyngitis, sore
throat, and rhinitis. (Otitis media, nausea,
seizures, diarrhea, and vomiting among
children. ) not coryza (runny nose).
Spread： via aerial droplets and fomites.
Incubation：1-4 days.
Onset : 5 days. (-1~7 days to spread)
Complications：Pneumonia, myositis,
encephalopathy, transverse myelitis, Reye
syndrome, myocarditis, and pericarditis.
Transmission of Influenza A Viruses
from Animals to People
 Influenza A viruses are found in
many different animals, including
ducks, chickens, pigs, whales,
horses, and seals.
 Wild birds are the primary natural
reservoir for all subtypes of influenza
A viruses.
 Pigs can be infected with both
human and avian influenza viruses
in addition to swine influenza viruses.
Hosts of Influenza A Virus
How the Flu Virus Can Change "Drift" and "Shift"
 antigenic drift: small changes in the virus
that happen continually over time. Every 2 – 3
years.
 antigenic shift: an abrupt, major change in
the influenza A viruses, resulting in new HA
and/or new HA and NA proteins in influenza
viruses that infect humans. Every 10 - 15
years.
Antigenic drift and shift
Avian Influenza (Bird Flu)
 Two surface antigens
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1. HA: 15 subtype from H1~H15.
2. NA: 9 subtype from N1~N9.
All subtypes can be found in wild birds.
Only 3 subtypes of HA (H1, H2 and H3) and
two subtypes of NA (N1 and N2) are
circulating widely in humans.
Avian influenza viruses do not usually directly
infect humans or circulate among humans.
Southern China is a hypothetical influenza
epicenter.
H5N1 Hong Kong Flu (1997)
More than 1
million chickens,
ducks, and geese
were killed in
Hong Kong , Dec.
1997.
Avian Influenza Infections in Humans
 1997: H5N1 infected both chickens and humans in
Hong Kong. 18 people were hospitalized and 6 of
them died. About 1.5 million chickens was killed.
 1999: H9N2 were confirmed in 2 children. Several
additional human H9N2 infections were reported from
mainland China in 1998-99.
 2003: More than 80 cases of H7N7 illness were
reported, and 1 patient died in the Netherlands. H9N2
infection was confirmed in a child in Hong Kong.
Avian Influenza Infections in Humans
2003-04 Avian Influenza Outbreak
 In birds: outbreak of H5N1 infection in
Cambodia, China, Hong Kong, Indonesia,
Japan, Laos, South Korea, Thailand, and
Vietnam.
In people: 33 cases of H5N1 infection in
Vietnam (23) and Thailand (10), 22 (15+7)
deaths have been reported.
Characteristics of Avian Influenza in
Birds
 Water birds act as hosts of influenza
viruses by carrying the virus in their
intestines and shedding it.
 Viruses in saliva, nasal
secretions and feces.
 Fecal-to-oral transmission
is the most common mode
of spread.
Characteristics of Avian Influenza in
Birds (cont.)
 Most influenza viruses cause no symptoms,
or only mild ones in wild birds; however, the
range of symptoms in birds varies greatly
depending on the strain of virus and the
type of bird.
 Infection with certain avian influenza A viruses
(e.g. some H5 and H7 strains) can cause
widespread disease and death among some
species of wild birds and especially
domesticated birds such as chickens and
turkeys.
Information on Influenza A (H5N1)
 Background:
1. H5N1 is a subtype of Type A influenza virus.
2. Wild birds are the natural hosts of virus.
3. 1st identified in Italy > 100 ys ago
isolated from birds (terns) in South Africa
in 1961.
Information on Influenza A (H5N1)
(cont.)
 Infection:
1. In 1997, 1st direct bird-to-human
transmission of H5N1 in Hong Kong;
caused illness in 18 people, of who 6
died. (Mortality is 30%). The outbreak
was halted in Hong Kong by slaughter of
the chickens.
2. But so far, H5N1 viruses
have not been capable of
efficient human-to-human
transmission.
Information on Influenza A (H5N1)
(cont.)
 Spread:
1. Infected birds shed virus in saliva, nasal
secretions and feces.
2. Avian influenza viruses spread among
susceptible birds when they have contact
with contaminated excretions.
3. Most cases of H5N1 infection in humans
have resulted from contact with infected
poultry or contaminated surfaces.
Current H5N1 Strain
 All genes are of bird origin.
 Different variations of H5N1 virus are
circulating at this time.
 H5N1 show antiviral resistance to
amantadine and rimantadine, but
oseltamavir and zanamavir should still
be effective.
Symptoms of Avian Influenza in
Humans
 Typical influenza-like symptoms (e.g.,
fever, cough, sore throat and muscle
aches).
 Eye infections, pneumonia, acute
respiratory distress, viral pneumonia,
and other severe and life-threatening
complications.
Prevention of Avian Influenza
 Prescription medications approved for
human influenza strains would be effective in
preventing avian influenza infection in
humans.
 Vaccination: The single best way to prevent
the flu is to get vaccinated each fall. In the
absence of vaccine, however, there are other
ways to protect against flu.
Other Habits for Good Health
 Avoid close contact.
 Stay home when you are sick.
 Cover your mouth and nose.
 Clean your hands.
 Avoid touching your eyes, nose or
mouth.
預防禽流感~ 衛生署
染病的活鳥和家禽的糞便中可能會帶有病毒，
故應盡量避免接觸活鳥和家禽及其糞便。如
曾接觸活鳥或家禽，要立刻用肥皂和清水洗
手。如家中飼養雀鳥，應避免和牠有親密接
觸，並每次在接觸牠或替牠處理糞便後用肥
皂和清水洗手。學校及幼兒院舍亦應採取措
施防止兒童接觸活鳥及家禽。出外旅遊時應
避免接觸活鳥及
家禽。進食家禽肉類和
蛋時應徹底煮熟。
 如有流感徵狀便要看醫生
，並要戴上口罩，以防傳
染他人。
工作人員如何避免受到感染？
 接種流感疫苗。
 若出現發燒、喉嚨痛、咳嗽等類流感症狀或眼睛發炎
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的現象，禁止接觸禽畜。
與禽畜接觸時需穿著長袖、不透水的工作服並需戴厚
橡膠手套。
配戴平面口罩，避免留在空氣不流通的工作場所。
建議使用護目鏡。
穿不透水（如：橡膠、聚氨酯材質）之工作鞋。
時常以肥皂清潔雙手，工作結束時雙手需消毒。
Treating the Avian Influenza
 Rest, drink plenty of liquids, avoid using
alcohol and tobacco, and take medication to
relieve the symptoms of flu.
 Antiviral Medications:
1. M2 inhibitors (amantadine and
rimantadine)
2. neuraminidase inhibitors (oseltamivir
and zanimivir).
All of these must be prescribed by a doctor.
Antiviral treatment lasts for 5 days and must
be started within the first 2 days of illness.
Potential for an Influenza Pandemic
 All influenza viruses can change.
 There is little or no immune protection
against them in the human population.
 It is possible that an avian influenza
virus could infect humans and spread
easily from person to person, an
“influenza pandemic”
could begin!!!
 established in 1952
Surveillance in the United States
 Three surveillance systems, coordinated and
maintained by CDC:
1. Weekly Pneumonia and Influenza Mortality
Chart (in 122 cities )
2. Epidemiologists' Reports of Influenza Activity
(state health departments)
3. Physicians' Reports of Influenza-like Illness
(about 260 physicians )
 The information from these surveillance systems
is published periodically by the CDC, and is
available on the Internet.
Percent of Respiratory Specimens Testing Positive
for Influenza,
NYS WHO and NREVSS Collaborating Laboratories
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流感及禽流感之因應措施--衛生署疾病管制局
1.遵循「流感期SARS防治作戰動員計畫」。
2.建立流感大流行防治作戰動員計畫（Pandemic Flu
Preparedness）。
3.針對雞、鴨、豬農施打流感疫苗。
4.加強各縣市養殖戶衛教及自主健康管理。
5.發燒病人進行禽畜接觸史之詢問調查，一旦疑似流感，
立即給予克流感。
6.2004年10月1日起，二歲以下兒童列入流感疫苗施打對象。
7.加強國際間農業與醫療部門之合作及聯繫。
8.加強機場海關入境者之體溫監控。
9.呼籲民眾減少不必要之東南亞旅遊，並避免接觸禽畜。
10.民眾若出現發燒咳嗽請戴上口罩並避免出入公共場所。
病毒即時檢測系統
呼吸道病毒檢體檢驗流程
禽流感、流感與SARS 臨床症狀區別
Thanks for your attention !