After more than a year since the Ebola pandemic appeared in West Africa, Liberia – one of the worst hit countries – has been declared free of the virus. However, the initial global response was not encouraging. Despite having the knowledge and technology needed to contain the outbreak, help was initially sluggish and poorly effective. This situation illustrates one of the major lessons from the history of pandemics: that they are strongly influenced by health inequalities.
Pandemics are epidemics that spread widely and cross borders. In many respects, the world is a safer place for those concerned about these emerging infectious diseases – advances in science, particularly molecular biology, information technology, and epidemiology give us unprecedented tools for understanding, tracking and managing emerging threats. However, the world is also more dangerous. Forces such as health inequalities and environmental deterioration are also increasingly driving the emergence and spread of infectious diseases. An example is the increasing risk of vector-borne diseases in Europe.
Pandemics to worry about
The last century has given us rich experiences to draw on. We’ve had pandemics caused by influenza, HIV/AIDS, SARS and now Ebola. Each of these can give us useful lessons to inform more effective prevention and control, for example with Ebola, the importance of basic infection control, and from AIDS, the critical need to engage with affected communities.
There are more than 1,400 known human pathogens. Almost all of them are capable of causing epidemics. There are also literally hundreds of animal diseases that have the potential to cross the species barrier causing new human pandemics, as SARS did in 2002-03. Then there is our increasing capacity to synthesise entirely new pathogens. But rather than focusing on individual diseases, it is often more useful to think about “pandemic scenarios” (see table below). Despite their diversity, pandemics can be grouped into a fairly small set of these scenarios based on functional characteristics, such as their established behaviour, origins and capacity to spread.
As well as the pandemic scenario, we also need to consider severity. The health impact of an infection is strongly influenced by the nature of the illness it causes, notably the risk of dying (case fatality risk). This consideration was apparent during the 2009 influenza pandemic which had a case fatality risk that was similar to seasonal influenza though it did infect a younger population resulting in more years of life lost.
Equipping for pandemics
Historical experience suggests that we have the scientific knowledge and technology to control most pandemics. These approaches include: effective surveillance and laboratory services; the capacity for a coordinated response; effective and widely available healthcare; and access to essential vaccines, pharmaceutics and other supplies. Using science to control pandemics was spectacularly demonstrated with SARS where national public health institutes appeared to be particularly important. The major pandemic that is still not controllable is pandemic influenza, though public health measures can slow its spread and high quality healthcare services can reduce mortality.
One of the greatest tools we have on our side is the International Health Regulations (IHR). In the wake of SARS and growing concerns about “bird flu”, this remarkable agreement was signed into international law in 2005 by all 193 members of the World Health Organisation. It provides a blue-print for international cooperation to manage threats such as pandemic diseases. A key feature is that it specifies a model for effective global public health surveillance including an agreed approach to risk assessment of emerging threats.
However, these advances in technology are not available to all. As the Ebola pandemic has demonstrated, we still cannot deliver the simple measures needed to control such epidemics in a timely and effective way to all populations that need them.
What more is needed?
To reduce the risk from pandemic diseases we need both the capacity to respond effectively to these events when they occur and, ideally, the ability to prevent them starting in the first place. It is clear that the full potential of the IHR has not yet been realised. Many resource-poor countries have not yet been able to build the surveillance and response capacity outlined in this framework. Similarly, the WHO does not appear to have the resources and mandate to fully support responses within resource-poor countries that do not have sufficient infrastructure to manage pandemics themselves.
The pandemic scenario approach is also useful in that it starts to make us think in a more integrated way about other pandemic threats that need attention, such as the rise in antimicrobial resistance. There are benefits in trying to integrate thinking in this way as effective responses to different pandemics generally require very similar capabilities.
Experience of pandemics show that a common threat can unify the international community based on shared self-interest and hopefully also a commitment to humanitarian ideals. The capacity building required to prevent pandemics also overlaps with wider development needs, such as those described in the Millennium Development Goals.
Understanding the lessons from the history of pandemics – and applying these lessons – can support the global challenges of improving health equity and environmental sustainability. For example, finding ways of supporting sustainable food production could reduce reliance on bushmeat consumption, meet health equity and sustainability goals as well as reducing vulnerability to emerging zoonotic diseases such as Ebola. Achieving such development goals is challenging. However, there is a huge collective benefit in the greater health security that would result.