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| Journal of the New Zealand Medical Association,
03-July-2009, Vol 122 No 1298
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Influenza A(H1N1)09: New Zealand’s response to
the pandemic threat
Lance C Jennings
In April 2009 a novel influenza A(H1N1) virus came to the
world’s attention when it caused outbreaks in humans in Mexico and USA.
Within 2 weeks, New Zealand’s public health authorities were being
challenged. The return of a group of schoolchildren with symptoms of influenza
to Auckland on April 25 from Mexico triggered the activation of New
Zealand’s Influenza Pandemic Action Plan
(NZIPAP).1
On April 29, the World Health Organization (WHO) raised the
pandemic threat to Phase 5 followed by New Zealand declaring it a notifiable and
quarantinable disease on April 30. The WHO was initially reluctant to declare a
pandemic, largely based on the perceived mildness of the disease. However, with
the obvious widespread community spread in Southern Hemisphere countries
entering their traditional influenza seasons, the WHO declared a Pandemic (Phase
6) on June 11.2 New Zealand has responded to
this threat with perhaps one of the country’s largest public health
responses ever attempted.
The perception that the pandemic being caused by the novel
(H1N1)09 virus is trivial is of concern. Influenza can be a serious disease, and
annually we are affected by seasonal influenza outbreaks and epidemics of
varying severity, population burden in terms of absenteeism from school or work,
and individual burden in terms of severe illness, hospitalisation, and death. On
average, 300 New Zealanders die each year directly or indirectly as a result of
influenza. The virus associated with the current pandemic is causing illnesses
with classic influenza signs and symptoms of mild to moderate severity
(including high fever, headache, malaise, and cough—often with nausea,
vomiting, and diarrhoea).
Estimates of up to 50% of the population being infected by
this virus over the coming months will undoubtedly be associated with increasing
numbers of people (especially those with underlying medical conditions) with
severe illness requiring hospitalisation and possibly dying from this virus. We
should not become complacent about this novel A(H1N1)09 virus, because influenza
A viruses have a track record of unpredictability, however at the same time we
should not panic as the threat can be managed with strong Ministry of Health and
Government leadership.
The virusThis novel virus was dubbed “swine influenza” by
the media because of the virus’ origins from known swine influenza A virus
lineages. Several influenza A virus subtypes circulate in pigs (e.g. H1N1, H1N2,
H3N1, H3N2) causing a highly contagious acute respiratory disease, but they
rarely infect humans. However since 1998 a North American triple reassortant
H1N1 swine virus has been circulating and associated with human infections.
Analysis of the newly emerged A(H1N1)09 virus has shown that
6 of the viruses 8 genomic segments were derived from the North American swine
virus, with the 2 remaining segments being derived from Eurasian swine
viruses.3,4 Through these reassortments, this
virus has gained the ability to spread efficiently between humans.
Characteristically influenza A viruses become genetically
unstable when they move out of their natural host and continue to evolve. Ten
clades of A(H5N1) ‘avian’ virus have evolved and are now circulating
in domestic poultry since this viruses movement away from it’s natural
aquatic avian host in 1996. Historical data from the 1918 pandemic suggest that
the A(H1N1) ‘Spanish’ virus caused a mild wave, followed several
months later by a second pandemic wave associated with increased pathogenicity.
The question remains as to whether this A(H1N1)09 virus will
return as successive waves of seasonal influenza as with the 1957 H2N2 and 1968
H3N2 pandemic viruses, or will it return with increased pathogenicity? (the
sting in the “scorpion’s” tail so to speak).
New Zealand’s pandemic responseContainment strategies—New
Zealand’s pandemic planning has evolved since 1997 (when it was initially
a response framework) to the operational Action Plan (NZIPAP) of
today.1,5,6 The phases of this plan are
straightforward, with initial efforts focused on containment: “keeping it
out” and “stamping it out”.
Following the entry into New Zealand of the first confirmed
cases on April 25, the response focus was on border management with the
identification and follow-up of symptomatic international travellers and their
immediate contacts. Controls at international airports—along with the use
of isolation, quarantine, and oseltamivir (Tamiflu™) for treatment of
laboratory confirmed cases and prophylaxis of their contacts—appeared to
delay community transmission of this novel virus through May into June.
This situation may have reflected the virus’s inherent
epidemiological characteristics which we do not fully understand. Regardless, it
bought valuable time to strengthen the public health services' frontline
capacity, the diagnostic capacity in the countries' five virology laboratories,
and other aspects of the primary, secondary health care, and other government
department’s responses.
Pivotal to the public health response was the laboratory
identification of the novel (H1N1)09 virus. Molecular tests (RT-PCR) were (and
remain) the most sensitive assay for the detection of this virus. Initial
identification involved the exclusion of seasonal influenza A(H3N2) and (H1N1)
subtypes, and confirmation by genetic sequencing, however by the second week of
May New Zealand virus laboratories were able to specifically identify the
(H1N1)09 virus and shorten the time for result availability to within 24 hours.
Rapid influenza antigen detection methods, including the rapid antigen tests
(RAT)7 and direct fluorescent antibody (DFA)
tests have been shown to be less sensitive and of restricted value.
Both border management and containment strategies are not
widely supported by the WHO, except containment at the source of the emergence
of a novel virus.8 New Zealand is well placed
as it is an island nation and has a well developed pandemic action plan and
public health infrastructure. For these reasons, the early distribution of
public health information with clear instructions on what travellers should do
if they developed influenza symptoms within 7 days of travel on all flights into
New Zealand, and the placing of clearly identifiable public health staff at all
international airports, were achievable and actively carried out.
The cases identified were largely individuals developing
symptoms who contacted the public health service or their general practitioner,
triggering the vigorous public health follow-up, respiratory sample collection,
laboratory confirmatory testing, and subsequent contact tracing of confirmed
cases. This approach was apparently successful for 6 weeks. Could we have done
better?
It is interesting to review the maritime quarantine
strategies carried out in the Pacific region during the 1918/19 pandemic. The
Western Samoa maritime quarantine was broken in 1918 by the SS Tahune,
from Auckland resulting in the introduction of virus and a 22% mortality, while
neighbouring American Samoa maintained full quarantine which kept the virus out
until 1921. No deaths were recorded in American
Samoa.9 This is clearly supportive of our
border management approach.
In 2008 an Otago University Pandemic Influenza Research
Group undertook a very extensive research project funded by the US CDC to assess
screening methods for influenza in arriving airline passengers. A pilot study by
Duncan and colleagues,10 and subsequent main
study outcomes which included an initial screening of more than 18,000
passengers arriving at Christchurch International Airport from
June–September 2008 (not yet published), clearly are in support of New
Zealand’s border management. Results indicate that it is at least feasible
to also detect people with influenza symptoms at our international
borders.
Management strategies—The rapid
spread of A(H1N1)09 in Victoria, Australia during the last week of May and
continuing global spread placed increasing pressure on the countries ‘keep
it out’ strategy. By the week of June 16 it become clear that community
spread was occurring in Auckland, Wellington and Christchurch, and containment
efforts were stressing both the public health service and virology services.
Movement to the “management” phase of New Zealand’s response
was not announced until June 19, however.
Although swine flu clinics were already in action in more
severely affected communities of Christchurch and Wellington, this allowed the
establishment of community-based assessment centres (CBACs) and the response to
focus on individuals more severely affected by influenza and needing antiviral
treatment or hospitalisation.
Wellington, closely followed by Christchurch, were the first
communities in New Zealand to experience an escalation in community
transmission. A possible reason for this may relate to the specific communities
initially affected. In Christchurch, the (H1N1)09 virus was introduced into the
Samoan community on about June 3 by a member of that community returning from
Melbourne with the virus. The subsequent amplification of infection amongst this
closely linked community probably then resulted in the seeding of schools, work,
and other communities in Christchurch, followed by exponential spread through
the community.
In Wellington, communities in Porirua and Wainuiomata have
been severely affected, clearly indicating that this virus is amplified in
socioeconomic communities were crowding may exist. In Canada, outbreaks of
(H1N1)09 amongst indigenous Inuit Indians were associated with severe disease
and hospitalisation, providing a clear warning that certain New Zealand Pacific
Island and Māori populations may also be at greater risk from this
virus.
Pharmaceutical preparednessPharmaceutical interventions, which include antivirals and
vaccines, clearly separate our ability to respond to the current pandemic as
compared to influenza pandemics in the past, particularly the 1918–19
pandemic.
New Zealand’s pandemic preparedness planning has
ensured that an antiviral (oseltamivir) stockpile, sufficient treatment doses
for 31% of the population has been put in place. Oseltamivir from the stockpile
has been used extensively during the containment phase, and now for the
treatment of more serve illnesses during the management phase. Individuals
travelling to affected countries have also been able to access oseltamivir by
prescription, placing pressure on the private market supplies.
Pharmacy distribution of oseltamivir to individuals with
influenza symptoms through pharmacist prescribing (a novel strategy pioneered
with seasonal influenza over the past two winters) has been
reviewed.11 It has been proposed that
Pharmacists should be able to make a clinical evaluation by telephone, rather
than the currently required face-to-face clinical evaluation. This strategy
would complements the commonsense advice to stay at home if you are sick.
Because of international concerns about the development of
resistance in the (H1N1)09 virus to oseltamivir, and the co-circulation of
seasonal (H1N1) virus known to be resistant to oseltamivir, the national
stockpile has been reviewed and now contains zanamivir (Relenza™). The
development of widespread resistance of the seasonal influenza A(H1N1) virus to
oseltamivir (through the H275Y mutation) is not believed to be directly linked
to drug usage, although drug induced resistance can occur. To date, drug induced
resistance has resulted in viruses which are unable to spread and are of no
clinical relevance. It is prudent though to maintain virological surveillance
and flexibility in our pharmaceutical response strategies, especially as
oseltamivir resistance in an A(H1N1)09 viral isolate has now been
reported.12
Our best protection against influenza is receiving an
influenza vaccine; however, pandemic vaccines with current technologies cannot
be produced until the novel pandemic virus has emerged, and are unlikely to be
commercially available for 4 to 6 months and after the first wave of a
pandemic.13 As part of the NZIPAP, a
100,000-dose stockpile of influenza A(H5N1) whole virus cell-culture derived
pre-pandemic vaccine, and a forward purchasing agreement with CSL for the supply
of an egg-derived split virus pandemic vaccine, are in place.
Vaccine manufacturers are expected to have influenza
A(H1N1)09 vaccines available from August 2009.Their availability following the
likely peak of our New Zealand pandemic should not delay any decision to acquire
such a vaccine however it will inevitably delay any decision to utilise such a
vaccine. Indeed, this may be to our advantage, it will allow more time for human
trial data to become available, and a more complete safety and efficacy
assessment to be made by Medsafe.
Looking to the futureOf major concern is our inability to predict the evolution
of influenza A viruses, especially now that there is an additional novel
influenza A virus capable of causing disease in humans which is spreading
globally.
The simple concept of influenza A virus evolution through
point mutations (as with antigenic drift) or through gene reassortment
(antigenic shift) may be more complex and also involve other genetic
recombination events.14
The circulation among humans globally of this novel
A(H1N1)09 virus along with seasonal H1N1 and H3N2 viruses—and in parallel
the highly pathogenic A(H5N1) and A(H9N1) avian viruses in domestic poultry
(both of which are capable of causing human infections associated with high
mortality) and the swine influenza A lineages—is possibly unprecedented
We must not become complacent about influenza and continue
pandemic preparedness activities at all levels in our community. The education
initiatives on basic respiratory hygiene among school children, such as the
‘Sneeze Safe’ programme (www.sneezesafe.co.nz) and handwashing and
social distancing (staying at home when you have symptoms of influenza) will
have longer term benefits to the health of New Zealanders.
Similarly, initiatives by the National Influenza Strategy
Group (NISG) have seen an unprecedented increased uptake of seasonal influenza
vaccine, which in the face of the co-circulation of seasonal H1N1 and H3N2
viruses, will lessen the likelihood of individuals suffering from multiple
influenza A virus infections.
New Zealand is also well placed to contribute to the global
research efforts on influenza to understand these viruses, their evolution and
the disease that they cause The call for a research agenda has been made and
pandemic research priorities identified,15
however little progress has been made toward achieving this.
Early on in this pandemic, New Zealand had the third largest
number of cases globally, however our focus (and rightly so) was on mounting a
public health response. Had a research capacity been identified in advance,
optimal use of the collected case history, epidemiological, surveillance and
virological data could have been made more widely available and especially to
the international community.
A review of our national efforts to keep out, contain and
manage this novel (H1N1)09 pandemic will be essential as our experience will not
only benefit the further evolution of our pandemic action plan, but also the
global community, especially the Northern hemisphere countries as they enter
their winter influenza seasons.
Competing interests: None known.
Author information: Lance C Jennings,
Clinical Associate Professor, University of Otago, Christchurch (and Canterbury
Health Laboratories, Christchurch)
Correspondence: A/Prof Lance Jennings,
Canterbury Health Laboratories,
PO Box 151, Christchurch 8011, New Zealand. Fax: +64 (0)3 3640075; email: lance.jennings@cdhb.govt.nz References:
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