epidemic-network

Turning points in history can be identified with certainty only with the benefit of hindsight. The signs are, however, that [we are] at a key moment in the history of mankind’s struggle against infectious diseases
Lancet Infectious Diseases, Editorial

This year saw the sad passing of the leading medical anthropologist and historian, George Armelagos. In a widely cited 1996 paper, Armelagos argued that the emergence and resurgence of disease was the result of the interaction of some or all of the following factors:

  • global social, demographic, and environmental changes
  • international trade, travel and technological change
  • breakdown of public health measures
  • the adaptations and genetics of microbes

The relevance of this framing to current patterns of diseases becomes clear when we look at current examples of infectious disease threats. Consider the following four stories, all drawn from the last two weeks:

  • The Centre for Disease Control announce that US measles cases are at a 20 year high, with outbreaks occurring among unvaccinated clusters of people exposed to travellers bringing the measles virus back from other countries – most notably the Philippines, where a large outbreak began in October 2013.
  • The World Health Organization confirms that the Ebola outbreak in West Africa has reached Sierra Leone, and that control of the disease – which has no known vaccine or cure and is suspected to originate from bats and transferred to humans through bushmeat production processes – is inadequate to the scale of the problem.
  • The UAE government revises upwards its estimates from deaths related to MERS – the Middle Eastern variant of SARS, which recently reached European and American shores  – while researchers find evidence that the MERS virus is identical to one that also kills camels, and worrying reports emerge about the proximity of MERS incidence sites in Saudi Arabia with the hajj routes for 4 million pilgrims travelling to Mecca.
  • The UK Chief Medical Officer, Dame Sally Davies held a briefing at the Royal Society in which she provided data showing that 5,000 deaths a year in the UK, and over 25,000 across Europe, were due to drug-resistant diseases. In America, the mortality figures for hospital-acquired infections alone top 99,000.

These stories usefully illustrate the different ways in which the drivers described by Armelagos have combined to raise disease incidence and impacts around the world. Of course, disease is far from being the only outcome of these drivers. We live in an era of unrivalled human influence on the planet – what some have called the ‘anthropocene’. The UN has described the physical and ecological changes wrought by globalisation as ‘the most fundamental transformation triggered by human civilisation since rise of agriculture’.

It is perhaps no coincidence, then, that in subsequent studies Armelagos compared our modern disease landscape to precisely the one humanity faced ten millennia ago, when we started moving away from hunter-gatherer lifestyles and toward more settled lives. The agricultural revolution, like the current global revolution, saw humans radically change their environment. We started to live in more continuous contact with animals, and with each other. From this period, we began to be afflicted by many major diseases that are still prevalent in developing countries today: measles, small pox, influenza, mumps, cholera – the list goes on.

Starting in the 19th century and continuing through much of the 20th, it seemed as though we were gaining the upper hand over the assembled legions of our microbial enemies.Thanks to modern medical advances, disease was being conquered, or at the very least, firmly controlled. We had antibiotics to treat bacterial infections, vector control programmes to prevent parasitic diseases, and vaccinations to deal with viruses. In 1969 the US Surgeon General William H Stewart reported to Congress that it was time to “close the book on infectious diseases”.

As an editorial in the inaugural Lancet Infectious Diseases put it, rather dryly:

Perhaps he [Stewart] should have known better. For infectious diseases are caused by living things, and living things are unpredictable and adapt to adverse environments. Organisms that occur in vast numbers and pass through many generations in a short time mutate and adapt quickly (10 billion bacteria will have mutations in about 1000 loci) relative to the plodding pace of human progress. As is human nature, confidence in our eventual victory over infectious diseases led to complacency, a complacency that pathogens were swift to exploit.

Today, despite  – or perhaps because of – the optimism of the mid-late 20th century, things look quite different to Stewart’s infamous prediction. Many diseases that we had thought to be under control are coming back with a vengeance, including TB, malaria, cholera, pneumonia and West Nile disease. Over the past 20 years,  strains of common microbes such as Staphylococcus aureus and Mycobacterium tuberculosis have continued to develop resistance to the drugs that once were effective against them. And there are worrying instances of disease emergence, some of which we barely understand: HIV-AIDS being by far the most significant, but also Ebola and other haemorrhagic fevers, hepatitis C, SARS, MERS and MRSA. A WHO report published in 2007 warned that infectious diseases are spreading more rapidly than ever before, and that new infectious diseases are emerging and re-emerging at a faster rate than any time in history.

How big a problem is this globally? According to CSIS, 16% of all deaths globally each year are due to infectious diseases. This of course varies changes by risk group and by country income levels. In 2010, researchers at John Hopkins found that infectious diseases cause almost two-thirds of all under 5 deaths globally. Based on calculations of WHO data and the charts below, we can see that the infectious disease burden is disproportionately borne by developing countries: while it may be a re-emerging problem in rich countries, it is safe to say that in poorer countries the problem never really went away.

– in low income countries, 38% of all deaths and 6 of the top 10 causes of death are accounted for by infectious diseases

WHO-data

– in low-middle income countries, 24 % of all deaths and 5 of the top 10 causes of death were due to infectious diseases

WHO-data-1

– in high income countries, 4% of all deaths and 1 of the top 10 causes of death were due to infectious disease

WHO-data-2

This data may justify a degree of complacency for those in rich countries. But even in high-income countries, as Dame Sally Davies has argued, infectious diseases cannot be dismissed. In the UK in 2011, infectious and parasitic diseases were responsible for over 200,000 admissions to National Health Service hospitals in England , and this was an increase of 10% on the previous year, and 84% since 2007, confirming a clear rising trend.

This overall scenario is an echo of what leading epidemiologist David Waltner-Toews once described to me as a new major global challenge: an ‘epidemic of epidemics’.

So what should we be doing in response? Last month, a number of top scientists argued that the evolution of microbes in the face of medical treatments is “in many ways… similar to climate change. Both are processes operating on a global scale for which humans are largely responsible.”  The same paper bemoaned the “feeble” international response to date, and called for a new intergovernmental panel to address the problem.

The idea is that, just like the IPCC, the proposed new panel will bring together global expertise to fight the drastic threats posed by the resistance of microbial pathogens of all kinds – from HIV and malaria to MRSA and TB . This new body is seen as vital because no single existing organisation is seen to have the breadth of knowledge or scope necessary to deal with the problem.

We will have to wait and see whether this call will have any traction in a global policy landscape which is already overburdened with conflicting priorities. Judging by the experience of the IPCC, even if such an institution is successfully established, we will not be closing the book but merely at the start of a new chapter in our ages-old battle against infectious diseases.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

About Ben Ramalingam

I am a researcher and writer specialising on international development and humanitarian issues. I am currently working on a number of consulting and advisory assignments for international agencies. I am also writing a book on complexity sciences and international aid which will be published by Oxford University Press. I hold Senior Research Associate and Visiting Fellow positions at the Institute of Development Studies, the Overseas Development Institute, and the London School of Economics.

Category

Antimicrobial resistance, Disease, Epidemics