Monday, December 17, 2007

The World Health Organization on the Health Effects of Climate Change

Margaret Chan, Director-General of the World Health Organization, has made the health effects of climate change the theme for WHO this year. Last week she made a major address on the topic. I quote extensively:
At the start of this century, a group of British journalists ran a competition for the best fictitious story that might depict what lies ahead during this century. Here is one of the winners: “Heads of state, meeting today on the tropical island of Switzerland, have reached consensus. Predictions of global warming have no foundation in science.”

My, how things have changed. The power of scientific research has triumphed. The verdict is in. Climate change is real. Human activities are a prime cause. The consequences are already being felt in ways that can be measured. Humanity will suffer, for some decades to come, for past sins in the way we have inhabited this planet.

As the climate scientists tell us, even if greenhouse gas emissions were to stop today, the consequences will be felt throughout this century. In the language of the scientists, human activities have committed this planet to climate change. The emphasis now is on the ability of our human species to adapt to changes that have become inevitable.

The warming of the planet will be gradual, but the increasing frequency and severity of extreme weather events – intense storms, heat waves, droughts, and floods – will be abrupt and the consequences will be acutely felt.

The health sector must add its voice – loud and clear – to the growing concern. Just as we fought so long to secure a high profile for health on the development agenda, we must now fight to place health issues at the centre of the climate agenda. We have compelling reasons for doing so. Climate change will affect, in profoundly adverse ways, some of the most fundamental determinants of health: food, air, water.

This is the reality that concerns me the most. Developing countries will be the first and hardest hit. Subsistence agriculture will suffer the most. Areas with weak health infrastructures will be the least able to cope.

Imagine the impact on health in areas where the food supply is already precarious, rural areas are populated with subsistence farmers and the capacity to cope with any emergency is already fragile.

Imagine the situation in cities, when water scarcity combines with heat stress and air pollution. We already have good evidence linking such conditions to increased deaths from respiratory and cardiovascular disease, especially in the elderly.

As the scientists tell us, the nature of climate change during this century is likely to go beyond human experience. But public health has abundant experience as a basis for interpreting the health consequences and understanding their impact. Public health has decades of experience in dealing with problems that will be made bigger and broader by climate change.

Ladies and gentlemen,

When I announced to my staff that I had selected climate change as the theme for next year’s World Health Day, I described climate change as the defining issue for public health during this century.

Let me take this statement one step further today. I have given my impressions about the public health landscape of today, the difficult challenges we face, but also the many reasons for unprecedented optimism.

I believe that climate change will ride across this landscape as the fifth horseman. It will increase the power of the four horsemen that rule over war, famine, pestilence, and death – those ancient adversaries that have affected health and human progress since the beginning of recorded history. Research already has a great deal to say about the impact of climate change on famine and pestilence.

Let us consider famine, hunger, food security, and malnutrition. In many parts of the world, the severe adverse effects of climate change – one could say, the catastrophic effects – are not expected to be felt until around the middle of this century or even later.

Not so for Africa. According to the latest projections, Africa will be severely affected as early as 2020. This is just a dozen years away. By that date, increased water stress is expected to affect from 75 million to 250 million Africans. A dozen years from now, crop yields in some countries are expected to drop by 50%.

Imagine the impact on food security and malnutrition. In many African countries, agriculture remains the principal economic activity, and agricultural products are the principal source of export trade. Vast rural populations survive, hand-to-mouth, on subsistence farming. There is no surplus. There is no coping capacity. Yes, as I said, these are catastrophic effects.

Concerning pestilence, abundant evidence links the distribution and behaviour of infectious diseases to climate and weather. As the scientists say, climate defines the geographical distribution of infectious diseases. Weather influences the timing and severity of epidemics.

Diseases transmitted by mosquitoes are particularly sensitive to variations in climate. Warmth accelerates the biting rate of mosquitoes and speeds up maturation of the parasites they carry. Sub-Saharan Africa is already home to the most severe form of malaria and the most efficient mosquito species. What will happen if rising temperatures accelerate the lifecycle of the malaria parasite? What if malaria spreads to new areas?

NIH funded the landmark study that demonstrated a link between climate variability and increased malaria epidemics in the highlands of East Africa. We all know about the explosive epidemic potential of malaria when this disease reaches non-immune populations. Though we are making progress, we are still not able, right now, to achieve adequate population coverage with preventive interventions in areas of stable malaria transmission.

The landmark publication on microbial threats, issued in 1992 by the Institute of Medicine, opened the eyes of the world to the growing menace of emerging diseases. It also showed how changes in the way humanity inhabits this planet have created abundant opportunities for microbes to exploit.

It is easy to see how climate change will increase these opportunities in significant ways. When we consider the effects of climate change on emerging diseases, we are looking at disruptions to intricately balanced ecological systems that reached equilibrium following centuries of evolution. Nature gives us every reason to believe that disruption of this delicate equilibrium will have profound consequences.

Consider the emergence of hantavirus pulmonary syndrome in the south-west of this country in 1993. The appearance of that disease has been linked to a 10-fold increase in the mouse population, which followed an unusual weather event that killed off species that prey on mice. We see what can happen when weather disrupts an intricate ecosystem.

Let me give you another example of what might be in store. As noted in the November climate report, El-Nino driven bush fires and drought, as well as changes in land use and land cover, have caused extensive alterations in the habitat of bat species that are the natural reservoir of the Nipah virus.

Let us look at the health consequences. The disease emerged in 1999 in Malaysia among pig farmers. Close contact with pigs, the intermediate host, was quickly identified as the risk factor. Then came the first consequence.

The disease was initially misdiagnosed, by a WHO Collaborating Centre, as Japanese encephalitis. This misdiagnosis was caused by the co-infection of a patient with Japanese encephalitis and Nipah virus. The diagnosis led to a hugely expensive, disruptive and useless containment effort directed at mass vaccination and mosquito control.

Pigs and people continued to die. Confidence in the government plummeted. Malaysian scientists isolated the virus and identified Nipah as a new disease. That solved part of the problem.

Altogether 265 cases and 105 deaths occurred, with an overall case fatality rate of 39%. Investigation of the outbreak found no evidence of human-to-human transmission.

Case closed? Not at all. In 2001, the virus resurfaced in India and Bangladesh. In Bangladesh, outbreaks are now recurring annually according to a seasonal pattern. Evidence from these outbreaks indicates that the virus has become more pathogenic for humans.

The case-fatality rate has risen to almost 75%. Contact with pigs is no longer necessary. Human-to-human transmission, also after only casual contact, has been documented. In one case, a rickshaw driver died of the disease after transporting a patient to hospital. Furthermore, transmission within hospital settings is now strongly suspected.

In one outbreak, consumption of fresh date palm juice, contaminated by bat saliva or faeces, has been identified as the vehicle of transmission in several fatal human cases. So from a zoonosis, to human-to-human, to foodborne in a very short time. Fortunately, up to now, outbreaks have occurred in sparsely populated rural areas, thus limiting their size.

Let me make one personal comment on the issue of new diseases. Initial misdiagnosis is the norm when new diseases emerge. They are, by definition, poorly understood. The US initially misdiagnosed the first cases of West Nile fever as St Louis encephalitis. I was in charge of the health department in Hong Kong when SARS emerged.

My life long, I will never forget the agony of uncertainty as Hong Kong scientists worked day and night to determine what was killing our doctors and nurses, what microscopic beast had invaded our hospital system. Then as now and in the future, doctors and nurses are at the frontline when a new disease emerges. Then and in the future, they put their lives at risk.

Let us turn to the impact of climate on war and death. We know that competition for resources, and especially competition for scarce water, has been a so-called “war starter” on many occasions in the historical past.

Some argue that the consequences of climate change may provoke an increasing number of conflicts. I do not know. But I certainly know what conflict and complex emergencies mean for health.

WHO has had offices in Darfur for the past four years. Many attribute the origins of this conflict to severe drought, followed by population movements and fierce competition for resources.

I know another thing, too. Many of the unspeakable atrocities that affect civilians in this conflict occur when women and young girls leave the safety of refugee camps in their desperate search for firewood. In this scorched and barren land, it may take them two days to gather sufficient firewood. Two days at risk of sexual violence and mutilation. This is the utter desperation.

Let us look at death, and let us do so from a public health perspective. Public health looks especially hard at preventable deaths. This is my greatest personal concern. Climate change could vastly increase the current huge imbalance in health outcomes. Climate change can worsen an already unacceptable situation that the Millennium Development Goals were explicitly and intricately designed to address.

Let me remind you. The Millennium Declaration and its Goals are all about fairness. As stated: “Those who suffer or who benefit least deserve help from those who benefit most.” More specifically, the Declaration stresses fairness in a world that is being radically reshaped by the forces of globalization.

As stated: “The central challenge we face today is to ensure that globalization becomes a positive force for all the world’s people. For while globalization offers great opportunities, at present its benefits are very unevenly shared, while its costs are unevenly distributed.”

This is indeed the problem. Globalization creates wealth and this is good. But globalization has no rules that guarantee fair distribution of this wealth. Health and wealth are intricately linked. The consequences of inequity can be measured by the great and growing gaps in health outcomes. I believe that, in matters of health, our world is dangerously out of balance, possibly as never before.

No comments: