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? ? ? ? ? ? ? ? Avian Influenza; Bird Flu ?

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Avian Influenza; Bird Flu March 2, 2k4 – PowerPoint PPT presentation

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Title: ? ? ? ? ? ? ? ? Avian Influenza; Bird Flu ?


1
? ? ? ? ? ? ?? Avian Influenza Bird Flu ?
  • ??????????
  • ?????? ? ?
  • March 2, 2k4
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2
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.

3
Introduction Influenza A virus
  • Infect various animal hosts (avian, mammalian).
  • Serologic and genetic analysis
  • 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.

4
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.

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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.

9
Morphology of Influenza A virions
  • Orthomyxoviridae
  • spherical and 80-200nm in diameter
  • 8 segments of (-)ssRNA
  • "spikes" of haemagglutinin (HA) and neuraminidase
    (NA)

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12
Influenza A polypeptides
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14
The Life Cycle of Influenza Virus
15
Inactivation of Influenza A virus
  • Radiation
  • pHgt9 or lt5
  • Temp. above 50C (56C, 3h 60C, 30m)
  • Detergents and organic solvents
  • Drying in 2448 h
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16
Characteristics of Influenza
  • mortality 0.01
  • flu spread droplet spread.
  • flu season from late December through March.

17
Clinical Signs and Symptoms of Influenza
  • Fever, nonproductive cough, myalgia, 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.
  • Incubation1-4 days.
  • Onset 5 days. (-17 days to spread)
  • ComplicationsPneumonia, myositis,
    encephalopathy, transverse myelitis, Reye
    syndrome, myocarditis, and pericarditis.

18
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.

19
Hosts of Influenza A Virus
20
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.

21
Antigenic drift and shift
22
Avian Influenza (Bird Flu)
  • Two surface antigens
  • 1. HA 15 subtype from H1H15.
  • 2. NA 9 subtype from N1N9.
  • 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.

23
H5N1 Hong Kong Flu (1997)
More than 1 million chickens, ducks, and geese
were killed in Hong Kong , Dec. 1997.
24
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.

25
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 (157) deaths have
    been reported.

26
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.

27
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.

28
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 gt 100 ys ago
  • isolated from birds (terns) in South Africa in
    1961.

29
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.

30
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.

31
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.

32
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.

33
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.

34
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.

35
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36
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37
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38
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.

39
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!!!

40
  • established in 1952

41
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.

42
Percent of Respiratory Specimens Testing Positive
for Influenza,NYS WHO and NREVSS Collaborating
Laboratories

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45
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48
Thanks for your attention !
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