Feature

Global sneezes spread diseases

Globalisation of travel, food production and environmental degradation is increasing the threat from infectious diseases, old and new. Kelley Lee explains

There is a description in Richard Preston’s non-fiction book The Hot Zone in which Nancy Jaax, a veterinary surgeon in the American military, suddenly discovers a breach at the wrist of her biological space suit.¹ She is in the high-security laboratory of the US Army Medical Research Institute of Infectious Diseases where she is dissecting a crab-eating monkey imported from the Philippines.

The laboratory is designated biosafety level four, the highest level of security, known as the ‘hot zone’ because it is where biological weapons and highly lethal infectious diseases are handled. Jaax is investigating a potential case of Ebola and the moment when she finds that infected blood has seeped into her suit is terrifying. The panic she feels is palpable and we are no doubt intended to share her cold fear.

Reports of a global tuberculosis emergency in 1993, over 200 deaths from Ebola in Zaire in 1995 and public health panics over bubonic plague in India and Hong Kong flu in 1997 have inflamed our primeval fears of plague and pestilence.

We need a sense of proportion about these infections, balanced with an understanding of how globalisation may be changing the nature of infectious diseases and our vulnerability to them.

Historically, the worldwide spread of infectious diseases has coincided closely with a gradual process of globalisation over many centuries. Christopher Columbus’ arrival in the Americas in 1492 is seen by medical historians as a turning point. Along with an accelerated flow of people across continents came the exchange of infectious agents. Plague, typhus and influenza travelled along the trade routes between Asia and Europe, and then onwards by land and sea to spread throughout the old and new worlds.

Measles, polio and smallpox were introduced to the Americas by Europeans who, in turn, are thought to have brought syphilis home. Later, the flourishing slave trade brought hookworm, yaws, filariasis, leprosy and possibly schistosomiasis and malaria from Africa to the Americas.

It was from this period that medical historians date the advent of pandemics – that is, a higher than expected rate of disease occurring on several continents at once – as opposed to epidemics where excess disease is confined to a particular area.²

So what is it about recent history that has renewed our fears of infectious diseases? There is growing evidence that something different is happening, that diseases we thought defeated by medical science are re-emerging as a threat. These include plague, cholera, diphtheria, yellow fever, dengue and TB. Added to this is the spectre of newly emerging diseases. Some 30 new disease-causing organisms have been identified in the past 20 years, including HIV, hepatitis C, Ebola and rotavirus.

Globalisation from the late 20th century has also been distinct in a number of respects. The most obvious perhaps is the people’s greater movement: the advent of affordable air travel means that almost any destination in the world can be reached within 36 hours, less than the incubation period for most infectious diseases.

Over the past decade, visits abroad from the UK have increased by about 18 per cent a year. In 1997 alone, there were 46 million trips abroad by UK travellers, with nearly one million to Africa, 500,000 to the Indian subcontinent and 250,000 to South America. Globally, 625 million tourists (8 per cent of the world’s population) arrived in different countries around the world, with Europe receiving 60 per cent of these travellers.³

In addition to tourism, business and study travel, migration and displacement are moving people internationally at an unprecedented rate.

From medieval times, quarantine has been the main means of trying to protect populations from diseases transmitted across national borders. Today the sheer volume of people travelling and the trend towards more open borders in some regions, such as the European Union, pose obvious logistical challenges for the protection of public health.

Minor illnesses, such as the common cold, are routinely transmitted within the close confines of aeroplanes, where recycled air exposes all passengers to the sneezing and coughing of others. A far smaller, yet worrying number of reports of more serious illnesses including cholera (from infected aeroplane food) and TB warn us that our desire to travel far exceeds our readiness to deal with the potential health consequences of a globally mobile population.

As well as hyper-mobility, widening inequalities within and across countries are contributing to our vulnerability to infectious diseases. A billion people live in poverty worldwide, with three-fifths of the developing world lacking access to safe sanitation, a third lacking access to clean water and a fifth to health care of any kind.

The end of the Cold War has added to these numbers by pressuring former Communist governments to join the global economy at the cost of cutting public spending on health, education and housing. The so-called ‘emerging economies’ in eastern and central Europe have experienced particularly serious setbacks, as their basic social infrastructures have crumbled amidst political and economic instability. These countries are reporting worrying trends in the spread of infectious diseases among them multidrug resistant TB, HIV/AIDS and syphilis.

Another contributory factor to the global spread of infectious disease is environmental degradation. The appearance of newly emerging diseases has been linked with the destruction of rainforests and other natural ecologies.

One example was the discovery of a new strain of cholera (known as Bengal 0139) off the coast of Bangladesh in 1992, as a result of the huge levels of toxic waste dumped into local waters. Scientists are also studying global climate change and how this might lead to the spread of ‘tropical diseases’ such as malaria and dengue into the northern hemisphere.

Closely related to environmental changes are the ways in which we produce and process food. High-intensity farming methods, coupled with cost-cutting measures for feeding livestock, are blamed for the emergence and spread of bovine spongiform encephalopathy (BSE) and new variant Creutzfeldt-Jakob disease (nvCJD) in the UK. Crowded living conditions in the Far East, with people, pigs and poultry together in close quarters, are believed to be the cause of periodic mutation of the influenza virus.

The globalisation of food production and trade means that food-borne diseases can be transported rapidly to consumers worldwide. The insufficiently regulated use of antibiotics by farmers to raise livestock has also contributed to spreading antibiotic resistance.

Added to all this is the fact that current forms of globalisation are weakening our capacity to address infectious diseases in an effective and timely way. Globalisation currently places the individual accumulation of wealth above collective goals such as resource redistribution and social justice. The liberalisation of economies worldwide has demanded reduced public expenditure on, for example, health systems and the promotion of a global economy through multilateral trade agreements has, so far, given limited attention to its associated public health risks.

All of this adds up to a very worrying picture. But it is not Ebola that poses the greatest health threat but older, more familiar diseases, like TB. The best example, and one from which we are all at risk, is the next influenza pandemic. We accept ’flu as an annual inconvenience and for most people it is a relatively mild illness from which they recover after a week or two in bed. For this reason, we hear little about influenza other than annual news bulletins encouraging vulnerable population groups to have ’flu jabs and advising the rest of us how to deal with the symptoms should we fall ill.

But potentially influenza is a far more sinister illness and one that illustrates the role of globalisation in spreading infectious disease more widely and rapidly than ever before. Historical records suggest that influenza is one of the oldest and commonest diseases. But influenza pandemics have only been with us since around 1580. Pandemics occur at irregular intervals of between 10 and 40 years. The biological cause is a fundamental change in the virus, known as antigenic shift, which produces a new strain that can be lethal to a far greater proportion of the population.

There were three such pandemics during the 20th century: in 1918–19, 1957 and 1968. By far the deadliest was the so-called Spanish flu of 1918–19, which killed an estimated 20 to 40 million people. We are overdue for the next antigenic shift. Which takes us back to the question of perspective.

So should we be concerned? Yes, but we should not simply direct our fear outwards, to a world outside our own borders, a world apparently teeming with diseases ready to strike us down. The real reasons behind the globalisation of infectious diseases lie not in the exotic nor the tropical, but in our individual and collective lifestyle choices. The solution lies not in keeping the world out, but in locating ourselves more centrally in the world around us. Infectious diseases invariably demand collective responsibility. This is a much bigger challenge.