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12/2/2004 1
Modern Methods for Influenza Detection and Sub-typing
Ronald Cheshier
12/2/2004 2
Introduction Training provided by the CDC, Association of
Public Health Laboratories (APHL), and the National Laboratory Training Network (NLTN) October 25, 2004 to October 29, 2004 at the Georgia State Laboratory
This course provided up to date information on Influenza epidemiology, surveillance, and laboratory testing protocols. One of the primary goals was to encourage the State Laboratories to develop the tools necessary for rapid response to a Pandemic Influenza A scenario.
12/2/2004 3
Influenza Virus review
Family Orthomyxoviridae: three types
Influenza A Influenza B Influenza C (not considered of
critical importance) Segmented (8) ssRNA genome
with lipid envelop
12/2/2004 4
Influenza A
Further classified by Hemagglutinin (H) and Neuraminidase (N) sub-types
Current circulating strains are H1N1 and H3N2
Human subtypes include H1N1, H3N2, H1N2, and H2N2
Avian subtypes include H1 to H15 and N1 to N9
Bird human H5N1, H9N2, H7N7, H7N2, H7N3
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Influenza B
Produces less serious disease than does Influenza type A
Not categorized as by H or N type as Influenza A is
12/2/2004 6
Influenza C
First isolated in 1949 Not known to be responsible for
epidemics
12/2/2004 7
Anticipated circulating strains for 2004/05
Northern hemisphere A/Fujian/411/2002(H3N2)-like A/New Caledonia/20/99 (H1N1)-like B/Shanghai/361/2002-like
12/2/2004 8
Influenza as a public health threat Influenza Viruses are the respiratory
viruses of greatest public health importance, particularly Influenza A
12/2/2004 9
Epidemiology, Prevention, and Control of Influenza; esp. Influenza A
Why is Influenza A such a public health threat? antigen drift (variation within the HN sub-type) or antigenic
shift (variation between different HN sub-types) makes large portions of the population immunologically naïve on a regular basis
Influenza epidemics can be characterized as inter-pandemic or pandemic
Annual average US winter epidemics affect 5% to 20% of the population with approximately 200,000 influenza-related hospitalizations during the 1990’s and 36,000 influenza related deaths.
At one time it was thought that new HN variants were due to re-assortment of genetic material from an avian strain and a human strain in a third animal, like a pig. Modern evidence suggests that humans may act as this mixing vessel
12/2/2004 10
For example
A pig or person is infected with an avian influenza like an H5N4 at the same time the pig or person is infected with a human strain like H1N1;
During the infections the two genomes re-assort to an H5N1 (with the avian H and the human N)
12/2/2004 11
Global and US surveillance
Avian influenza: H5N1: HIGHLY PATHOGENIC
Present in Asia since 1996 Extent/distribution not firmly
established Threat level is high In 1997 there were 18 confirmed
cases of H5N1 with 6 deaths Other avian strains being watched
include H7N7 and H9N2
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Pandemic Influenza
Recipe for a human pandemic Emergence of a novel sub-type of
influenza to which the population is immunologically naïve
Replication in humans disease Efficient human-to-human
transmission Note: H5N1 has meet all criteria
except the third one.
12/2/2004 13
Pandemic planning
An influenza pandemic will be unlike other public health emergencies or common disasters.
Inevitable Will arrive with very little warning Locally explosive epidemics Widespread, not focused like a bio-
terrorism event Will put an extraordinary strain on human
and material resources Effect will be relatively prolonged –weeks
to months
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Laboratory issues
Laboratory safety Tissue culture techniques Rapid test kits HA/HI sub-typing Immuno-fluorescent testing Real time PCR analysis
Molecular typing and sub-typing
12/2/2004 15
Laboratory/Epidemiology Topics of Discussion
Reviewing current Influenza surveillance testing algorithm
Brief comments on alternative Influenza surveillance algorithms and the ability of this laboratory to support them.
12/2/2004 16
Current testing algorithm
Inoculation of specimens into cell culture; one diploid, one Hep-2, one Viromed Rhmk and two Diagnostic Hybrid Rhmk
In the absence of CPE, “blind” Hemadsorption (HAD) at days 7 and 14.
In the absence of CPE “blind” passage of Hep2 with “blind” FA for RSV at day 14 for all patients ≤5 years old
Identification of Influenza isolates: Immuno-fluorescent testing to identify
type (A or B) followed by Hemagglutination Inhibition (HI) testing to identify sub-type
12/2/2004 17
Alternatives to be considered
The use of shell vials for more rapid isolation and identification of Influenza Studies by Wisconsin and Iowa suggest that MDCK
shell vials are more sensitive for Influenza than Rhmk cell culture
MDCK shell vials inoculated, incubated, and “blind” stained at day 5 for Influenza A and B with supernatant saved and used for HI testing (if necessary).
Things to consider:• Cost: purchase shell vials commercially with goal
of preparing our own shell vials once the cell culture preparation method has been established.
• The CDC provides the FA reagents as part of the WHO/CDC Influenza Kits received each year. In addition, commercial sources are available.
• Time and labor requirements; Not an issue once Arbovirus season is over.
12/2/2004 18
Alternatives to be considered
The use of Immuno-fluorescence (IFA) for Influenza A sub-typing The CDC/WHO kit provides staining
reagents for H1N1 and H3N2 Cost: We would have to purchase
additional anti-mouse IgG conjugate commercially.
This procedure would decrease turn-around-time
Has the potential for allowing us to test for 2 sub-types at once by using different conjugates, I.e. FITC and Rhodamine
12/2/2004 19
Alternatives to be considered
Use of Rapid Test kits Things to consider
Cost: These kits are very expensive and have relatively short shelf-lives
Poor positive predictive values in the absence of an outbreak (high sensitivity but low specificity)
These kits are probably more effective for use at a primary care setting during influenza season
12/2/2004 20
Alternatives to be considered PCR: The CDC has provided the sequence data for the
primers and probes for Influenza A (group) and Influenza B (group). In addition, it has provided the data for H1, H3, and H5 (avian considered as possible candidate for next pandemic). Things to consider
Cost: While the cost of primers is probably manageable, probes are very expensive.
There will be a lag time as we will have to obtain all the probes and primers and do validation studies. This includes validation for H5; Note, we do not have any controls for that agent. The CDC has indicated they will provide a Proficiency set sometime next year.
The CDC primer sets are for H1, H3, and H5, not H1N1, H3N2, and H5N1 (no neuraminidases). The CDC is not overly concerned about this because it is the “H” (Hemagglutinin) that is related to pathogenicity but, if we choose to report based on PCR we will only be able to report on the Hemagglutinin result.
12/2/2004 21
Suggested algorithms It is not the intent of the CDC to replace culture with
PCR but rather to allow the States to have PCR testing available as a surveillance/rapid diagnostic tool
Isolation will still be needed for vaccine related surveillance and production efforts
Consider the purpose of this surveillance effort
12/2/2004 22
Next Steps
Laboratory Management and the State Epidemiology will have to meet to more carefully review and discuss the options available to us in terms of surveillance enhancement.
12/2/2004 23
Items to consider
It has been 20+ years since our Influenza algorithm has been changed
A number of exciting new methods and tools are available to us including The use of shell vials Immuno-fluorescent sub-typing including
multiplexing PCR
12/2/2004 24
Final algorithm
Should allow for the most rapid response possible
Cost considerations Sensitivity and specificity of the
tests Validation studies, not just to
satisfy CLIA requirements but also to ensure that the tests being performed are providing accurate information.
12/2/2004 25
Presented By:
Ron Cheshier, Virology Section Manager
Arizona Department of Health Services - Bureau of State Laboratory Services
(602) 542-6134 or cheshir@azdhs.gov
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