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| Journal of the New Zealand Medical Association,
11-March-2005, Vol 118 No 1211
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New Zealand’s preparedness for the next influenza
pandemic
Lance Jennings
Pandemic influenza is one of the most significant global
public health emergencies. Since late 2003, the avian influenza A (H5N1)
epizootic in Asia, which has affected both animals and humans, has brought the
world closer to an influenza pandemic than at any time since
1968.1,2
Avian Influenza in AsiaConditions favouring the emergence
of a pandemic virus are increasingly being met. The H5N1 virus is now endemic
amongst poultry in parts of Asia, has become increasingly pathogenic for
poultry, and is expanding its host range. The virus has caused the death of
tigers and domestic cats in Thailand and transmission between domestic cats has
been demonstrated experimentally. Wild waterfowl are the natural reservoir for
all influenza A viruses, however asymptomatic ducks have now been shown to
excrete the highly pathogenic H5N1 virus, thus providing another source for
infection.
H5N1 virus has been isolated from pigs on farms in China,
fuelling concerns of the possible emergence of a novel virus from this
source.3 Human cases have occurred in Thailand,
Viet Nam, and Cambodia during the three waves of avian influenza. Probable
human-to-human transmission has been reported in a family cluster in Thailand in
September 2004,4 and additional family clusters
have been identified in Viet Nam during January and February 2005, however
sustained human-to-human transmission has not been demonstrated.
The WHO call for pandemic preparednessSince this epizootic first came to
the world’s attention in January 2004, the World Health Organization
(WHO) has repeatedly encouraged all countries to undertake pandemic preparedness
activities,5,6 The WHO held an international
consultation in April 2004 on the public health interventions before and during
a pandemic.7 This meeting drew extensively on
the lessons learnt from the public health interventions used to contain the 2003
severe acute respiratory syndrome (SARS) outbreak. A second WHO consultation was
held in December 2004, and recommended several revisions to the WHO preparedness
plan for an influenza pandemic.6
The WHO plan presents a phased approach in which sequential
epidemiological events trigger a range of international and national activities.
Revisions focus on the inclusion of additional levels of alert and related
activities needed when a pandemic threat arises from an outbreak in animals. The
WHO, through its regional offices (WHO/WPR and WHO/SEAR), has been holding
pandemic planning workshops and is contributing to the development of a
pandemic-planning checklist.
Pandemic influenza in the previous century (1900–2000)When looking at the past history of
influenza, there is good reason to commit significant resources for global,
national, and regional pandemic planning. Over the previous century
(1900–2000) there have been three pandemics—beginning in 1918, 1957,
and 1968. The 1957
Asian and
1968 Hong Kong pandemics caused large
numbers of cases and a combined mortality estimated to be more than 3 million
deaths—mostly in the very young, the elderly, and people with underlying
chronic conditions. In contrast, the
1918–19
Spanish pandemic caused an estimated
50–100 million deaths, mainly in persons 15–35 years old.
Statistical modelling suggests that a future influenza
pandemic will cause 2–7 million deaths worldwide. The current mortality
rate of recognised human cases of avian influenza in Thailand and Viet Nam is
~70%. If there is a pandemic involving avian influenza , then deaths could be
dramatically higher.8 The 2003 SARS outbreak
gave the world a glimpse of the potential societal and economic disruption of
such an event. As New Zealand has been affected by past pandemics, it would be
unlikely to escape one in the future.
New Zealand’s Pandemic Action PlanNew Zealand has a pandemic action
plan, which has been incorporated within the
National Health Emergency Plan: Infectious
Diseases.9 We are one of only five
countries in the Asian-Pacific region with well-advanced pandemic planning and
implementation—many countries are yet to start.
Indeed, pandemic planning has been a part of New
Zealand’s influenza control strategy since the mid 1990s with the first
preparedness plan being in place in 1999. Initiatives such as the national
simulation exercise ‘Exercise Virex,’ and the utilisation of the
plan as the framework for the national SARS response, have helped challenge the
plan and have contributed to its evolution.
The establishment of the National Influenza Strategy Group
(NISG) (to promote influenza awareness and the use of seasonal influenza
vaccines), agreements for pandemic vaccine supply, and the recent establishment
of a stockpile of the influenza antiviral oseltamivir, are all integral parts of
the national strategy. However, the pandemic action plan must continue to be
viewed as a ‘living document’ so that it can be updated and
strengthened as new information becomes
available.10
The report included in this issue of the
Journal by Nick Wilson et al
(Estimating the impact of the next influenza
pandemic on population health and health sector capacity in New Zealand.
URL: http://www.nzma.org.nz/journal/118-1211/1346)
addresses the impact of another pandemic on New Zealand. Assessing the burden of
influenza on hospital admissions and mortality is difficult, as influenza
diagnoses are generally not laboratory confirmed and are often attributed to
pneumonia or other complications that occur following influenza infection.
The application of statistical modelling can provide a range
of estimates of potential impacts in terms of deaths, hospitalisations, and
outpatient visits due to pandemic influenza. Modelling helps to structure the
discussion on pandemic preparedness and facilitates the translation of pandemic
planning concepts to concrete plans.
Unfortunately nobody can predict when the next pandemic will
occur, nor can they accurately forecast who will become ill and suffer adverse
health outcomes such as death and hospitalisation. Nevertheless, the hosting in
Viet Nam of the 2nd International Meeting on
Avian Influenza Control in Animals (23–25 February 2005), jointly
organised by the Food and Agriculture Organization (FAO), the World Organization
for Animal Health (OIE), and the World Health Organization (WHO), has provided
yet another platform to bring this important public health issue to the
world’s attention.
Author information:
Lance C Jennings, Virologist, Canterbury Health Laboratories, Canterbury
District Health Board, Christchurch
Correspondence: Dr
Lance Jennings, Canterbury Health Laboratories, PO Box 151, Christchurch. Fax:
(03) 364 0750; email:
lance.jennings@cdhb.govt.nz
References:
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