The spread of bird flu has forced countries around the world to look at how they would tackle an outbreak.



Many have also developed plans to protect against the possibility that the virus will start to spread between humans.

The World Health Organization recommends countries should stockpile enough anti-viral drugs to cope with a pandemic, which it estimates would affect 25% of the population, but warns that developing countries in particular are likely to fall well short.

Responding to the avian influenza pandemic threat
WHO (pdf file)

excerpt:

Background
Influenza pandemics have historically taken the world by surprise, giving health services little time to prepare for the abrupt increases in cases and deaths that characterize these events and make them so disruptive. Vaccines – the most important intervention for reducing morbidity and mortality – were available for the 1957 and 1968 pandemic viruses, but arrived too late to have an impact. As a result, great social and economic disruption, as well as loss of life, accompanied the three pandemics of the previous century.

The present situation is markedly different for several reasons. First, the world has been warned in advance. For more than a year, conditions favouring another pandemic have been unfolding in parts of Asia. Warnings that a pandemic may be imminent have come from both changes in the epidemiology of human and animal disease and an expanding geographical presence of the virus, creating further opportunities for human exposure. While neither the timing nor the severity of the next pandemic can be predicted, evidence that the virus is now endemic in bird populations means that the present level of risk will not be easily diminished.

Second, this advance warning has brought an unprecedented opportunity to prepare for a pandemic and develop ways to mitigate its effects. To date, the main preparedness activities undertaken by countries have concentrated on preparing and rehearsing response plans, developing a pandemic vaccine, and securing supplies of antiviral drugs. Because these activities are costly, wealthy countries are presently the best prepared; countries where H5N1 is endemic – and where a pandemic virus is most likely to emerge – lag far behind. More countries now have pandemic preparedness plans: around one fifth of the world’s countries have some form of a response plan, but these vary greatly in comprehensiveness and stage of completion. Access to antiviral drugs and, more importantly, to vaccines remains a major problem because of finite manufacturing capacity as well as costs. Some 23 countries have ordered antiviral drugs for national stockpiles, but the principal manufacturer will not be able to fill all orders for at least another year. Fewer than 10 countries have domestic vaccine companies engaged in work on a pandemic vaccine. A November 2004 WHO consultation reached the stark conclusion that, on present trends, the majority of developing countries would have no access to a vaccine during the first wave of a pandemic and possibly throughout its duration.

Apart from stimulating national preparedness activities, the present situation has opened an unprecedented opportunity for international intervention aimed at delaying the emergence of a pandemic virus or forestalling its international spread. Doing so is in the self-interest of all nations, as such a strategy could gain time to augment vaccine supplies. At present capacity, each day of manufacturing gained can mean an additional 5 million doses of vaccine. International support can also strengthen the early warning system in endemic countries, again benefiting preparedness planning and priority setting in all nations. Finally, international support is needed to ensure that large parts of the world do not experience a pandemic without the protection of a vaccine.

Pandemics are remarkable events in that they affect all parts of the world, regardless of socioeconomic status or standards of health care, hygiene and sanitation. Once international spread begins, each government will understandably make protection of its own population the first priority. The best opportunity for international collaboration – in the interest of all countries – is now, before a pandemic begins.

Situation assessment

1. The risk of a pandemic is great. Since late 2003, the world has moved closer to a pandemic than at any time since 1968, when the last of the previous century’s three pandemics occurred. All prerequisites for the start of a pandemic have now been met save one: the establishment of efficient human-to-human transmission. During 2005, ominous changes have been observed in the epidemiology of the disease in animals. Human cases are continuing to occur, and the virus has expanded its geographical range to include new countries, thus increasing the size of the population at risk. Each new human case gives the virus an opportunity to evolve towards a fully transmissible pandemic strain.

2. The risk will persist. Evidence shows that the H5N1 virus is now endemic in parts of Asia, having established an ecological niche in poultry. The risk of further human cases will persist, as will opportunities for a pandemic virus to emerge. Outbreaks have recurred despite aggressive control measures, including the culling of more than 140 million poultry. Wild migratory birds – historically the host reservoir of all influenza A viruses – are now dying in large numbers from highly pathogenic H5N1. Domestic ducks can excrete large quantities of highly pathogenic virus without showing signs of illness. Their silent role in maintaining transmission further complicates control in poultry and makes human avoidance of risky behaviours more difficult.

3. Evolution of the threat cannot be predicted. Given the constantly changing nature of influenza viruses, the timing and severity of the next pandemic cannot be predicted. The final step – improved transmissibility among humans – can take place via two principal mechanisms: a reassortment event, in which genetic material is exchanged between human and avian viruses during co-infection of a human or pig, and a more gradual process of adaptive mutation, whereby the capability of these viruses to bind to human cells would increase during subsequent infections of humans. Reassortment could result in a fully transmissible pandemic virus, announced by a sudden surge of cases with explosive spread. Adaptive mutation, expressed initially as small clusters of human cases with evidence of limited transmission, will probably give the world some time to take defensive action. Again, whether such a “grace period” will be granted is unknown.

4. The early warning system is weak. As the evolution of the threat cannot be predicted, a sensitive early warning system is needed to detect the first sign of changes in the behaviour of the virus. In risk-prone countries, disease information systems and health, veterinary, and laboratory capacities are weak. Most affected countries cannot adequately compensate farmers for culled poultry, thus discouraging the reporting of outbreaks in the rural areas where the vast majority of human cases have occurred. Veterinary extension services frequently fail to reach these areas. Rural poverty perpetuates high-risk behaviours, including the traditional home-slaughter and consumption of diseased birds. Detection of human cases is impeded by patchy surveillance in these areas. Diagnosis of human cases is impeded by weak laboratory support and the complexity and high costs of testing. Few affected countries have the staff and resources needed to thoroughly investigate human cases and, most importantly, to detect and investigate clusters of cases – an essential warning signal. In virtually all affected countries, antiviral drugs are in very short supply. The dilemma of preparing for a potentially catastrophic but unpredictable event is great for all countries, but most especially so for countries affected by H5N1 outbreaks in animals and humans. These countries, in which rural subsistence farming is a backbone of economic life, have experienced direct and enormous agricultural losses, presently estimated at more than US$ 10 billion. They are being asked to sustain – if not intensify – resource-intensive activities needed to safeguard international public health while struggling to cope with many other competing health and infectious disease priorities.

5. Preventive intervention is possible, but untested. Should a pandemic virus begin to emerge through the more gradual process of adaptive mutation, early intervention with antiviral drugs, supported by other public health measures, could theoretically prevent the virus from further improving its transmissibility, thus either preventing a pandemic or delaying its international spread. While this strategy has been proposed by many influenza experts, it remains untested; no
effort has ever been made to alter the natural course of a pandemic at its source.6. Reduction of morbidity and mortality during a pandemic will be impeded by inadequate medical supplies.Vaccination and the use of antiviral drugs are two of the most important response measures for reducing morbidity and mortality during a pandemic. On present trends, neither of these interventions will be available in adequate quantities or equitably distributed at the start of a pandemic and for many months thereafter.

Outlined below are topics covered by the WHO document

Recommended Strategic Actions:

1. Reduce opportunities for human infection.
   • Support the FAO/OIE control strategy
   • Intensify collaboration between the animal and public health sectors
   • Strengthen risk communication to rural residents
   • Improve approaches to environmental detection of the virus
2. Strengthen the early warning system.
   • Improve the detection of human cases
   • Combine detection of new outbreaks in animals with active searches for human cases
   • Support epidemiological investigation
   • Coordinate clinical research in Asia
   • Strengthen risk assesment
   • Strengthen existing national influenza centres throughout the risk-prone region
   • Give risk-prone countries an incentive to collaborate internationally
3. Contain or delay spread at source.
   • Establish an international stockpile of antiviral drugs
   • Develop mass delivery mechanism for antiviral drugsC
   • Conduct surveillance of antiviral susceptibility
4. Reduce mortality, morbidity, and social disruption
   • Monitor the evolving pandemic in real time
   • Introduce non-pharmaceutical interventions
   • Use antiviral drugs to protect priority groups
   • Augment vaccine supplies
   • Ensure equitable access to vaccines
   • Communicate risks to public
5. Conduct research to guide response measures
   • Assess the epidemiological characteristics of an emerging pandemic
   • Monitor the effectiveness of health interventions
   • Evaluate the medical and economic consequences

Strategies for improving national preparedness:

1. Assist developing countries planning on manufacturing their own vaccines
2. Support national preparedness pandemic planning
3. Develop model pandemic reponse exercises

Strategies for expediting the development of a pandemic vaccine

1. Shorten the time between emergence of a pandemic virus and the start of commercial production
   • Develop global standards to ensure the quality, safety and efficacy of influenza vaccines
   • Resolve outstanding laboratory and safety issues
   • Harmonize regulatory pathways for licensure of pandemic influenza vaccines
   • Address safety issues associated with vaccine use
   • Support production strategies that economize on the use of antigen
2. Increase the supply of influenza vaccines
   • Find ways to bridge the gap between current vaccine production capacity and the expected demand during a pandemic
   • Involve vaccine manufacturers from all countries
   • Support efforts in developing countries, including through the use of technology transfer, for vaccine development and production
   • Enhance utilization of seasonal influenza vaccines in high risk groups, in line with WHO targets (50% coverage in 2006 and 75% in 2010)