SWINE INFLUENZA

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SWINE INFLUENZA

• PRESENTED BY
• DR.SUJA PILLAI
• IMD REPERTORY
• GHMC CALICUT

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WHAT IS SWINE INFLUENZA?

• Swine flu is a respiratory disease caused by
  influenza viruses that infect the respiratory
  tract of pigs.
• Swine flu produces most of the same symptoms in
  pigs as human flu produces in people.

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• Swine influenza is common in pigs in the
  midwestern United States , Mexico, Canada, South
  America, Europe (including the United Kingdom,
  Sweden, and Italy), Kenya, Mainland China,
  Taiwan, Japan and other parts of eastern Asia.

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HISTORY OF SWINE INFLUENZA

• The 1918 flu pandemic in humans was associated
  with H1N1 and influenza appearing in pigs, this
  may reflect a zoonosis either from swine to
  humans, or from humans to swine.
• Although it is not certain in which direction the
  virus was transferred, some evidence suggests
  that, in this case, pigs caught the disease from
  humans.
• For instance, swine influenza was only noted as
  a new disease of pigs in 1918, after the first
  large outbreaks of influenza amongst people.

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• Influenza viruses are classified within the
  family orthomyxoviridae.
• 3 viral subtypes A,B,C
• Viruses have 2 distinct surface antigens H and N

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ELECTRON MICROSOPE IMAGE OF H1N1 INFLUENZA VIRUS
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• Transmission of swine influenza virus from pigs
  to humans is not common
• When transmitted, the virus does not always cause
  human influenza and often the only sign of
  infection is the presence of antibodies in the
  blood, detectable only by laboratory tests

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• When transmission results in influenza in a
  human, it is called zoonotic swine flu. However,
  only about fifty such transmissions have been
  recorded since the mid-20th century when
  identification of influenza subtypes became
  possible.

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Why is swine flu now infecting humans?

• Influenza virus A is unique among the viruses
  because it is frequently subject to antigenic
  variation.
• First, the influenza viruses (types A, B, C) are
  enveloped RNA viruses with a segmented genome
  this means the viral RNA genetic code is not a
  single strand of RNA but exists as eight
  different RNA segments in the influenza viruses.
• A human (or bird) influenza virus can infect a
  pig respiratory cell at the same time as a swine
  influenza virus.

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• Various combinations of RNA segments can result
  in a new subtype of virus (known as antigenic
  shift that may have the ability to preferentially
  infect humans but still show characteristics
  unique to the swine influenza virus
• It is even possible to include RNA strands from
  birds, swine, and human influenza viruses into
  one virus if a cell becomes infected with all
  three types of influenza.
• Formation of a new viral type is considered to be
  antigenic shift

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• small changes in an individual RNA segment in flu
  viruses are termed antigenic drift and result in
  minor changes in the virus. However, these can
  accumulate over time to produce enough minor
  changes that cumulatively change the virus'
  antigenic makeup over time (usually years)

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• Antigenic shift appears to result from genetic
  recombination of human with animal or bird
  ,providing major antigenic change.This can cause
  a major epidemic or pandemic involving most or
  all age groups.

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• Since the isolation of virus in 1933 major
  antigenic change have occurred twice (1957-H2N2)
  and again in (1968-H3N3)
• Strains occuring between 1946 and 1957 have been
  called H1N1 strains.

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TRANSMISSION IN SWINE

• The main route of transmission is through direct
  contact between infected and uninfected animals.
• These close contacts are particularly common
  during animal transport.
• Intensive farming may also increase the risk of
  transmission, as the pigs are raised in very
  close proximity to each other.
• The direct transfer of the virus probably occurs
  either by pigs touching noses, or through dried
  mucus.
• Airborne transmission through the aerosols
  produced by pigs coughing or sneezing are also an
  important means of infection.
• Transmission may also occur through wild animals,
  such as wild boar, which can spread the disease
  between farms.

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TRANSMISSION IN HUMANS FROM SWINE

• People who work with poultry and swine,
  especially people with intense exposures, are at
  increased risk.
• Other professions at particular risk of infection
  are veterinarians and meat processing workers.

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TRANSMISSION FROM PEOPLE TO PEOPLE

• The main way that influenza viruses are thought
  to spread is from person to person in respiratory
  droplets of coughs and sneezes
• . This can happen when droplets from a cough or
  sneeze of an infected person are propelled
  through the air and deposited on the mouth or
  nose of people nearby.
• Influenza viruses may also be spread when a
  person touches respiratory droplets on another
  person or an object and then touches their own
  mouth or nose (or someone elses mouth or nose)
  before washing their hands.

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• Transmission of swine influenza virus from pigs
  to humans never occurs by eating properly cooked
  pork.

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SYMPTOMS IN SWINE

• In pigs influenza infection produces fever,
  lethargy, sneezing, coughing, difficulty
  breathing and decreased appetite.
• In some cases the infection can cause abortion.
  Although mortality is usually low (around 1-4),
  the virus can produce weight loss and poor
  growth, causing economic loss to farmers.
• Infected pigs can lose up to 12 pounds of body
  weight over a 3 to 4 week period

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SYMPTOMS OF SWINE FLU IN HUMANS
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COMPLICATIONS

• Pneumonia
• Respiratory failure
• Convulsions

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When to Seek Emergency Medical Care

• has difficulty breathing or chest pain
• has purple or blue discoloration of the lips
• is vomiting and unable to keep liquids down
• has signs of dehydration such as dizziness when
  standing, absence of urination, or in infants, a
  lack of tears when they cry
• has seizures (for example, uncontrolled
  convulsions)
• is less responsive than normal or becomes
  confused.

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PERIOD OF INFECTIVITY

• Persons with swine influenza A (H1N1) virus
  infection should be considered potentially
  contagious for up to 7 days following illness
  onset.
• Persons who continue to be ill longer than 7
  days after illness onset should be considered
  potentially contagious until symptoms have
  resolved.
• Children, especially younger children, might
  potentially be contagious for longer periods.

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DIAGNOSIS

• Swine flu is presumptively diagnosed
  clinically by the patient's history of
  association with people known to have the disease
  and their symptoms listed above.
• Usually, a quick test (for example,
  nasopharyngeal swab sample) is done
• Most of the tests can distinguish between A and
  B types.
• If the test is positive for type B, the flu is
  not likely to be swine flu (H1N1).

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• If it is positive for type A, the person could
  have a conventional flu strain or swine flu
  (H1N1).
• Swine flu (H1N1) is definitively diagnosed by
  identifying the particular antigens associated
  with the virus type.
• In general, this test is done in a specialized
  laboratory.

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• A confirmed case of swine influenza is obtained
  by
• real-time RT-PCR
• viral culture
• four-fold rise in swine influenza A (H1N1)
  virus-specific neutralizing antibodies

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RISK GROUPS

• Persons with certain chronic medical condition
• School children who are at high-risk for
  complications of influenza.
• Travelers to Mexico.
• Border workers
• Health care workers or public health workers

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PREVENTION

• Prevention in swine.
• Prevention of transmission to humans.
• Prevention of its spread among humans.

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PREVENTION IN SWINE

• Facility management
• using disinfectants
• ambient temperature to control virus in the
  environment. The virus is unlikely to survive
  outside living cells for more than two weeks,
  except in cold.

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HERD MANAGEMENT

• Includes not adding pigs carrying influenza to
  herds that have not been exposed to the virus.
• The virus survives in healthy carrier pigs for up
  to 3 months and can be recovered. Carrier pigs
  are usually responsible for the introduction of
  SIV into previously uninfected herds and
  countries, so new animals should be quarantined.

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VACCINATION

• Control of swine influenza by vaccination has
  become more difficult in recent decades, as the
  evolution of the virus has resulted in
  inconsistent responses to traditional vaccines.
• use of one of several bivalent SIV vaccines
  commercially available in the United States.

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PREVENTION IN HUMANS

• The transmission occurs due to close contact so
  farmers and veterinarians are encouraged to use a
  face mask when dealing with infected animals.
• Use of gloves when working with sick animals
• The use of vaccines on swine to prevent their
  infection is a major method of limiting swine to
  human transmission.

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• Frequent washing of hands with soap and water

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• Use of alcohol based sanitisers.

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• Use of
• towel while sneezing

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• Use of face masks

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VACCINE

• Although the current trivalent influenza vaccine
  is unlikely to provide protection against the new
  2009 H1N1 strain, vaccines against the new strain
  are being developed and could be ready as early
  as June 2009.

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TREATMENT

• In swine
• As swine influenza is rarely fatal to pigs,
  little treatment beyond rest and supportive care
  is required.
• Antibiotics are also used to treat this disease,
  which although they have no effect against the
  influenza virus, do help prevent bacterial
  pneumonia and other secondary infections in
  influenza-weakened herds.

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IN HUMANS

• Bed Rest
• Keep the sick person in a room separate from the
  common areas of the house.
• The U.S. Centers for Disease Controland
  Prevention recommends the use of Tamiflu
  (oseltamivir or Relenza (zanamivir) for the
  treatment and/or prevention of infection with
  swine influenza viruses.

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PROGNOSIS

• In general, the majority (about 90-95) of
  people that get the disease feel terrible but
  recover with no problems, as seen in patients in
  both Mexico and the U.S.
• Caution must be taken as the swine flu (H1N1) is
  still spreading and may become a pandemic.

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• Young adults have not done well, and in Mexico,
  this group currently has the highest mortality
  rate, but this data could quickly change.
• People with depressed immune systems
  historically have worse outcomes.

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• Another confounding problem with the prognosis of
  swine flu (H1N1) is that the disease is occurring
  and spreading in high numbers at the usual end of
  the flu season.
• Most flu outbreaks happen between November to
  the following April, with peak activity between
  late December to March

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• This outbreak is not following the usual flu
  pattern.
• Because swine flu (H1N1) does not seem to be
  following the usual flu disease pattern, any
  prognosis is speculative.

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• The first traceable case in Mexico, termed
  "patient zero," was a 5-year-old child in
  Veracruz who has completely recovered.
  Investigators noted that large pigfarms were
  located close to the boy's home
• The first death in the U.S. occurred in a
  23-month-old child who was visiting Texas from
  Mexico but apparently caught the disease in Mexico

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THANK YOU