Developing and sustaining a country's preparedness is challenging, and carries a risk of complacency.
Influenza pandemics are unpredictable but recurring events that can have severe consequences on societies worldwide. Since the 16th century, influenza pandemics have been described at intervals ranging between 10 and 50 years4 with varying severity and impact ().
CHARACTERISTICS OF THE THREE PANDEMICS OF THE 20th CENTURY.
The precise timing and impact of a future influenza pandemic remains unknown. Developing and sustaining a country's preparedness is challenging, and carries a risk of complacency.
Pandemic preparedness in most, if not all countries, remains incomplete - even though an influenza pandemic could occur at any time resulting in:
rapid spread of pandemic disease leaving little time to implement ad hoc mitigation measures;
medical facilities struggling to cope with a possible large surge in demand;
potentially serious shortages of personnel and products resulting in disruption of key infrastructure and services, and continuity of all sectors of business and government;
delayed and limited availability of pandemic influenza vaccines, antivirals and antibiotics, as well as common medical supplies for treatment of other illnesses;
negative impact on social and economic activities of communities which could last long after the end of the pandemic period;
intense scrutiny from the public, government agencies, and the media on the state of national preparedness; and
a global emergency limiting the potential for international assistance.
2.1. How influenza viruses with pandemic potential develop
Many animal influenza viruses naturally infect and circulate among a variety of avian and mammalian species. Most of these animal influenza viruses do not normally infect humans. However, on occasion, certain animal viruses do infect humans. Such infections have most often occurred as sporadic or isolated infections or sometimes resulted in small clusters of human infections.
An influenza pandemic occurs when an animal influenza virus to which most humans have no immunity acquires the ability to cause sustained chains of human-to-human transmission leading to community-wide outbreaks. Such a virus has the potential to spread worldwide, causing a pandemic.
The development of an influenza pandemic can be considered the result of the transformation of an animal influenza virus into a human influenza virus. At the genetic level, pandemic influenza viruses may arise through:
genetic reassortment: a process in which genes from animal and human influenza viruses mix together to create a human-animal influenza reassortant virus;
genetic mutation: a process in which genes in an animal influenza virus change allowing the virus to infect humans and transmit easily among them.
2.1.1. The highly pathogenic avian influenza A (H5N1) virus and an influenza pandemic
In 1997, an avian influenza A virus of subtype H5N1 first demonstrated its capacity to infect humans after causing disease outbreaks in poultry in Hong Kong SAR, China. Since its widespread reemergence in 2003-2004, this avian virus has resulted in millions of poultry infections and over four hundred human cases. An unusually high percentage of human H5N1 infections result in severe illness and death compared to other influenza viruses and far exceed the proportion of deaths caused by the 1918 pandemic virus. On rare occasions, H5N1 has spread from an infected person to another person - most often a family or other household member acting as a caregiver. However, none of these events has so far resulted in sustained community-level outbreaks.
The primary risk factor for a human to acquire a zoonotic H5N1 infection is direct contact or close exposure to infected poultry, although the virus remains difficult to transmit to humans. Five years after the widespread emergence and spread of H5N1, the virus is now entrenched in domestic birds in several countries. Controlling H5N1 among poultry is essential in reducing the risk of human infection and in preventing or reducing the severe economic burden of such outbreaks. Given the persistence of the H5N1 virus, successfully meeting this challenge will require long-term commitment from countries and strong coordination between animal and human health authorities.
While the H5N1 virus is currently the most visible influenza virus with pandemic potential, it is not the only candidate. Wild birds form a reservoir for a large number of other influenza viruses and influenza viruses are found in other animal species as well. Any one of these other viruses, which normally do not infect people, could transform into a pandemic virus. In addition to H5N1, other examples of animal influenza viruses previously known to infect people include avian H7 and H9 subtypes and swine influenza viruses. The H2 subtype, which was responsible for the 1957 pandemic (but has not circulated for decades), could also have the potential to cause a pandemic should it return. The uncertainty of the next pandemic virus means that planning for pandemic influenza should not exclusively focus on H5N1, but should be based on active and robust surveillance and science-based risk assessment.
2.2. Ensuring ethical pandemic preparedness and response
An influenza pandemic, like any urgent public health situation, calls for making certain decisions that will require balancing potentially conflicting individual interests with community interests. Policymakers can draw on ethical principles as tools to assess and balance these competing interests and values. An ethical approach does not provide a prescribed set of policies. Instead, it applies principles such as equity, utility/efficiency, liberty, reciprocity, and solidarity in light of local context and cultural values. While application of these principles sometimes results in competing claims, policymakers can use these principles as a framework to assess and balance a range of interests and to ensure that overarching concerns (such as protecting human rights and the special needs of vulnerable and minority groups) are addressed in pandemic influenza planning and response. Any measures that limit individual rights and civil liberties must be necessary, reasonable, proportional, equitable, non-discriminatory, and not in violation of national and international laws.8
WHO has developed9 detailed ethical considerations on priority setting, disease control measures, the role and obligations of health-care workers, and a multilateral response to pandemic influenza.
2.3. Integrating pandemic preparedness and response into general emergency preparedness
Pandemic preparedness activities take place within the context of national and international priorities, competing activities, and limited resources. Given the fundamental uncertainties surrounding the timing of the next influenza pandemic, steps to ensure the long-term sustainability of pandemic preparedness are crucial and should involve:
integration of pandemic influenza preparedness into national emergency preparedness plans, frameworks, and activities;
use of pandemic preparedness activities to strengthen basic and emergency health-related capacities (such as the primary health-care system, respiratory disease surveillance, and laboratory diagnostic capacities);
use of preparedness activities to actively build communication channels between sectors and communities;
development or modification of business continuity plans specifically tailored to pandemic influenza; and
periodic reassessment and updating of current plans based on new developments and information gained from exercises.
Through the use of these and other approaches, governments, public health agencies, and others have an opportunity to strengthen preparedness for the next influenza pandemic while building the capacity to address a range of local, national, and international emergencies.
- 4
Avian influenza: assessing the pandemic threat. Geneva, World Health Organization, 2005 (WHO/CDS/2005.29).
- 8
25 Questions and Answers on Health and Human Rights. Health and Human Rights Publication Series Issue No.1, July 2002. World Health Organization. ISBN 92 4 154569 0, p 18.
- 9
Ethical considerations in developing a public health response to pandemic influenza (WHO/CDS/EPR/GIP/2007.2), World Health Organization, 2007.
