Influenza and other respiratory viruses

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Influenza and other respiratory viruses

• Dr. Sue Huang
• Head, WHO National Influenza Centre
• Institute of Environmental Science and Research
• (Infection control nurses conference, 15 August
  2007)

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• Enveloped, segmented, negative-strand RNA virus
• Polymerase genes (3) PA, PB1, PB2
• Nucleocapsid genes (3) NP, NS1, NS2, M1, M2
• Glycoproteins genes (2) HA, NA

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Types and subtypes

• Type A, B, C
• Influenza A subtypes
• Wild aquatic birds--- 16H, 9N
• Human AH1N1 and AH3N2
• Viral strain is nomenclatured based on host,
  geographic location, laboratory strain number and
  year of isolation
• A/chicken/VietNam/1194/2004 (H5N1)
• A/Wellington/1/2004 (H3N2)

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Influenza viruses replicate in the columnar
epithelial cells of the respiratory tract Good
sampling should aim at maximizing the harvest of
virus-infected columnar epithelial cells.
Location Sample Nose nasal swabs, NPS,
NPA Throat swabs, washes Larynx washes,
aspirates Trachea aspirates, washes Bronchus
bronchoalveolar lavage (BAL) Lung biospy,
tissue

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Laboratory diagnosis

• Rapid antigen test
• Immunofluorescence
• Tissue Culture
• hemagglutination (HA) and hemagglutination
  inhibition (HAI)
• Polymerase chain reaction (PCR)

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Rapid Antigen test

• BD Directigen EZ Flu AB test
• Chromatographic assay
• Nucleoprotein of influenza A or B binds
  anti-nucleoprotein antibodies which is conjugated
  to visualizing particles and is shown as a pink
  line on the membrane.
• Fast, but lack sensitivity

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Immunofluorescence
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Tissue Culture
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Haemagglutination and haemagglutination
inhibition tests
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• Real time PCR (Taqman)
• 1 copy of DNA
• after 35 cycles 23668
• billions copies
• Quick 30 min to 1.5 hour

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Advantages and disadvantages of diagnostic methods
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Aims of National Influenza Surveillance

• describe incidence and distribution of influenza
• detect influenza epidemics to assist public
  health intervention
• identify the predominant strains to help plan for
  effective influenza vaccines.

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Laboratory-based Surveillance
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Influenza isolates by type
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Influenza vaccine recommendation
Aim achieve a close antigenic match between the
vaccine and circulating strains

• Epidemiological evidence
• Virological evidence
• Serological evidence

• WHO recommendations (2) northern and southern
• Australia Influenza Vaccine Committee (AIVC) New
  Zealand, Australia, South Africa
• Influenza Vaccine Formulation (3) AH1N1, AH3N2
  and B

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Vaccine recommendations for NZ, 1998-2006
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Vaccination policy

• In 1997, vaccine free to 65 years
• In 1999, extend to risk groups lt65 years

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Influenza mortality rates and vaccine update
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Respiratory Syncytial Virus

• ssRNA(-) virus
• Nonsegmented
• Enveloped
• Paramyxoviridae (family), Pneumovirinae
  (subfamily)
• Two groups A B
• respiratory illness, particularly in children
  during the winter time

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Annual laboratory confirmed RSV, 1990-2006
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Parainfluenza Virus

• ssRNA(-) virus
• enveloped
• nonsegmented
• 5 serotypes 1, 2, 3, 4a and 4b
• Paramyxoviridae (family), Paramyxovirinae
  (subfamily)

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Adenovirus

• ds DNA virus
• non-enveloped
• Adenoviridae (family)
• At least 47 serotypes are known
• classified into 6 subgenera A to F

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Enterovirus

• ssRNA () virus
• Non-enveloped
• Nonsegmented
• Picornavirus (family)
• more than 67 serotypes
• Serotype Polioviruses 3 Coxsackie
  A 23 Coxsackie B 6 Echoviruses
  31 Enteroviruses 4
• Can cause respiratory illness.

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Rhinovirus

• ssRNA() virus
• Picornavirus (family)
• acid-labile
• at least 100 serotypes are known

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Coronavirus

• ssRNA() Virus (30kb)
• Enveloped
• nonsegmanted
• pleomorphic morphology
• Coronaviridae (family)
• 2 serogroups OC43 and 229E
• newly identified viruses SARS and NL-63

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Human metapneumovirus (hMPV)

• ssRNA(-) virus
• Nonsegmented
• Enveloped
• Paramyxoviridae (family), Pneumovirinae
  (subfamily)
• cause influenza-like illness in very young,
  elderly and immunocompromised patients