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Tuesday 23 March 1999
I returned from a brief summer vacation - during which I did nothing good for the health of my skin – to find awaiting me the invitation from John Zillman asking me to deliver this address. I felt immensely honoured to have been asked and hastened to accept even if I cannot pretend to be a real expert on the health effects of weather and climate change, or on meteorology.
I did, however, begin my career by studying tropical public health at the Harvard School of Public Health many moons ago. This provided me with a life long interest in the very diseases that appear to be increasing around the world partly as the result of changes in our climate. Later in my career as Chief Medical Officer in both the New South Wales and Federal Health Departments I was to come face to face with public health emergencies involving climate related diseases and illnesses.
The topic "Weather, Climate and Health" is an enormous one on which a great deal has been written particularly in the last decade. I shall not be attempting to summarise the literature nor will I try to add to the excellent reviews already prepared by people like Tony McMichael of the University of London and Paul Epstein of Harvard. I do however want to take much of what these authors have said and – in the light of so many " scientific uncertainties" – ask what measures can or should national and international agencies realistically take to prevent further public health disasters. All of this too coming at a time in world history when budgetary pressures on public health systems are greater than ever before.
My own involvement began I suppose, soon after I took up the job as Chief Medical Officer in NSW towards the end of 1983. It coincided with the biggest epidemic of “ Epidemic Polyarthritis” – more commonly known as Ross River Fever – Australia had ever had. It was centred on the town of Griffith in the Murrumbidgee Irrigation Area of NSW over the period October 1983 to June 1984 with 60% of the incidence occurring in January and February. Many thousand people were affected although only 1196 were confirmed by laboratory studies. Public anxiety was very high and there were strident demands being made by politicians and the press for an immediate public health response.
There had been abnormally heavy rainfall in the affected areas coming at the end of a prolonged drought and the rains were accompanied by plagues of mosquitoes. Heavy use of larvacides in the rice fields and personal protection measures were partially effective but the epidemic did not finally disappear until cooler autumn weather arrived.
The National Health and Medical Research Council, of which I was a member, had begun to express concern about the potential interrelationships between climate and health in the mid eighties, and it put out a report on the potential hazards of the depletion in the Ozone Layer in 1989. We also commissioned work on a report on the Health Implications of Long Term Climate Change that was published in its final form in 1991.
The draft version of the latter report was run off in 1990 in time for me to have it in my back pocket for limited distribution at the Second World Climate Conference in Geneva that year which I attended in company with John Zillman and his meteorological colleagues. This Conference also coincided with the publication and launch by the World Health Organization (WHO) of their first report on the subject entitled “Potential health effects of climate change”.
It turned out that health received but scanty mention during the conference and these two documents and a small discussion group in a break out session were the only evidence of recognition that the world could be facing serious public health disasters from global warming.
I have three lasting recollections from that conference. The first concerned the indoor climate in the Geneva conference hall. Having been accustomed to WHO meetings where smoking had been banned for many years I was appalled by the plumes of tobacco smoke emanating from cigars, pipes and cigarettes! I hope the world’s meteorologists have reduced their own exposure to carcinogens in recent years!
The second thing that made an impression on me was the presentations made on the polar ice cores which seemed to me to offer firm evidence of relatively recent Greenhouse Gases (GHG) accumulation and temperature change portending disaster for the planet in the not too distant future.
The third event was a brush with fame in the form of David Suzuki who showed up towards the end of the conference to do numerous interviews with key presenters and delegates. He asked me what I thought the implications of all that I had heard were for human health. I recall saying that I was feeling distinctly uneasy about what I, as a mere public health administrator, had felt the meteorological presentations meant. I compared my feelings to those I had experienced in the very early days of the HIV/AIDS pandemic around 1983/1984 when everyone knew there was a problem but no one had isolated the causative virus nor had any real idea of the exact prevalence of the disease.
In Australia you may recall, wild estimates were being made by some self- proclaimed experts that over 100,000 of our citizens were already infected. The national numbers proved to be wrong (fortunately) but those visionaries like the late Jonathan Mann were proven absolutely correct in their predictions of an international health catastrophe. 1990, the year of the Second World Climate Conference, was also the year we hosted the first AIDS in Asia and Pacific conference in Canberra and no one at that meeting would have accurately predicted the extent of HIV incursion into Asia that has happened subsequently.
Are we facing the same sort of catastrophe with regard to climate change and health? In 1990 I feared that we were but today I am not so sure. Are the experts “crying wolf” and demanding unrealistic responses from government and international agencies, or will they be shown to be right? Recent events seem to indicate that we already could be in trouble in a number of respects:
As 1999 dawns, the meteorologists tell us that 1998 was the hottest year on record. Algal blooms (cyanobacteria), giardia and cryptosporidia threaten the potability of our water supplies. Japanese encephalitis threatens to gain a toehold on the Australian mainland for the first time ever.
In 1997 my former neighbour at WHO regional meetings, the Minister of Health for Brunei, was sacked for failing to prevent the health effects of the disastrous forest fires in Kalimantan on his constituency! These may be the results either of genuine climate change or manifestations of climatic variability coupled with our mismanagement of the environment. We need to know for certain.
We also need to know whether – as Brian Tucker said in this address two years ago – human populations can plan effectively to adapt to the changes that will confront the planet.
I would like to devote most of this address to looking at some of the evidence so well summarised in the superb 1996 WHO/WMO/UNEP publication edited by McMichael, Haines, Sloof and Kovats, entitled “Climate Change and Human Health”. (You will find a picture of its front cover on the Bureau of Meteorology’s beautiful calender for 1999).
This, plus additional evidence, will be discussed briefly in order to try and come to some conclusions as to likely outcomes and the action national and international agencies may need to take to prevent further deterioration in global public health. Let us consider a few key issues.
Humans have demonstrated amazing ability over the centuries to adjust to life under extreme weather conditions. There seems to be no doubt that physiological adaptation to hotter climates is possible but does not occur instantaneously. People living in warm climes can handle excessive heat better than those from normally colder ones.
An increase of one degree in the annual average temperature may not seem too alarming, but it does mean that at the extreme upper range, maximum temperatures will be fairly intolerable and possibly drawn out over many days or weeks.
The demographic tidal wave pushing populations into bigger and bigger cities will increase the “heat island” effect described in conurbations, adding further heat stress to vulnerable groups. These latter groups are the aged, the very young, and persons with serious pre existing illnesses. People from lower socioeconomic strata – those least able to afford insulation or air conditioning - are most at risk.
The 1980, 1983 and 1988 heat waves in the USA resulted in 1700, 556 and 454 deaths respectively. The length of the heat wave is an important factor in influencing the number of deaths from heat stroke or heat stress. In the 1987 heat wave in Athens the hospital admission rate and mortality rose more than fivefold after the third day of extreme heat.
However, recent research in the USA has demonstrated that as many as one third of heat wave related deaths occurred in people who would probably have died anyway within the next few weeks.
What are we to do in the face of this information? We need to continue our efforts to limit Green House Gases (GHGs), but in the short term there are some very practical steps that can be taken. Obviously the whole world cannot afford air conditioning but governments can – as in the Australian Capital Territory – use incentives to ensure that both new and existing homes are better insulated.
Air conditioning has many advantages, the major ones being to make living in hot climates more comfortable and to enhance productivity at work. It does however bring its own particular problems and it is no exaggeration to say that Legionnaires disease is largely a man made and climate made illness. Most of the cases are caused by the inhalation of bacteria in aerosols given off from poorly maintained cooling towers.
I was involved in one such epidemic at the end of a hot summer in the middle of the 1980s in the city of Wollongong during which 12 people died. A whole ward of the hospital was filled with patients whose chest X-rays looked like photographs of miniature snowstorms. The city was in a state of panic and you can imagine the sorts of pressure we had to work under to try and identify the source of infection. In fact we contained the epidemic by ordering all air conditioning plants in Wollongong to be turned off, and it was some time later that we identified the source of infection as a small poorly maintained cooling tower on top of the pharmacy in the main shopping mall. The owner of he shop swore his air conditioner had never been used that summer but it turned out that a locum who ran the shop once a week turned it on during very hot days!
In 1996 the total number of cases of Legionnaires disease in Europe was 1,566 which was several hundred more than previous years. Most of the excess was due to an outbreak in Spain which along with other warm countries like France and Greece had the highest incidence rates.
At the other end of the temperature spectrum it is argued that if global warming continues deaths from exposure to extreme cold will diminish. A recent British study has predicted that if winter temperatures increase by 2 or 2.5 degrees C there would be 9000 fewer winter-related deaths annually by 2050. On the other hand, by the same date it is postulated that the frequency of extremely hot days in cities like Washington DC will increase several fold.
Obviously close monitoring of the situation will be required over the next decade to see how well populations can acclimatise and modify their living and working arrangements.
People living in very hot and often poor situations already will be grossly disadvantaged if temperatures rise by only a little. I am thinking particularly, of remote desert communities where rising temperatures may exacerbate drought conditions. Water for important recreational swimming and sanitation may be impossible to find and potable water will become scarce.
In other parts of the world droughts subsequent on climate warming will have serious effects on crops and animal husbandry with consequent nutritional implications. Witness the disastrous El Nino engendered drought in Papua New Guinea a year or so ago. The spectre of huge numbers of drought related “environmental refugees” with all the attendant problems of violence and disease is something that also must be taken very seriously.
The effect of air pollution when combined with increasing temperatures has both short term and long term implications. In the short term serious respiratory disease in times of temperature inversion can be fatal. Unlimited growth of cities prone to inversions together with uncontrolled motor exhaust and incineration of garbage will inevitably result in periodic acute loss of life, to say nothing of illness and discomfort in breathing.
The World Bank in 1998 put out a press release concerning air pollution in Asia’s megacities following two decades of unparalleled and uncontrolled growth with unchecked emissions from automobiles, factories, domestic heating, cooking and refuse burning. Health and economic costs are estimated to be hundreds of millions of dollars. In Jakarta, Bangkok and Manila where transport is a major cause of air pollution the problem is particularly bad.
In many Chinese cities where reliance on coal is heavy, air quality is very poor and costs of pollution-related sickness and death are high. If global warming can bring warmer winters to China, less coal would need to be burnt – but better to act to provide better or more efficient combustion to reduce the volume of particulate matter going into the air. A week in December 1997 in Xian demonstrated to me clearly the very real hazards of severe air pollution.
The long term effects of air pollution are now coming to light, in that it is now considered that previously healthy persons may gradually develop a chronic disease that will shorten their lives. Chronic lung disease and cardiovascular disease appear to be related to pollution and the long-term inhalation of particulate matter. Further research is needed to elucidate the exact relationship but again there is no reason to delay taking remedial public health action.
Extreme Weather Events – floods, storms, droughts, and fires.
We seem to be much more conscious these days of disasters around the world and our evening TV news hardly allows us any respite. The tidal wave in PNG and the floods in central China and Central America come to mind as major disasters in 1998. The previous year there were severe droughts in PNG and South East Asia with concomitant fires and food shortages. Western Fiji was hit by a cyclone this January.
Loss of life, property and income all result from these tragedies and in the case of China many tens of thousands of “floating” people were forced to flee to the eastern seaboard in search of a new beginning.
Are these events increasing in number and if so how many can be said to be due to changes caused by human activity? Some studies have claimed that the frequency of these events has increased over recent decades. However the Inter Governmental Panel on Climate Change (IPCC) has concluded that there is no clear evidence of such an increase.
This does not mean however that we have to resign ourselves to inaction. Those countries (Bangladesh) or parts of countries (Central China) most prone to flooding must be assisted to take the necessary steps to protect their populations. In advance of El Nino Southern Oscillation (ENSO) events, countries susceptible to droughts and fires need to be forewarned. The same applies in reverse to periods of La Nina.
Floods and storms will continue to cause death through drowning and trauma, and many infectious diseases can arise in their aftermath as a result in the breakdown of basic sanitation. Disaster preparedness needs attention from all governments but blaming it all on global warming does not seem to be warranted at this point in time.
Sea Level Rise
Half the world’s population lives within 60 kilometres of the sea and sixteen of the 23 cities that have more than 10 million inhabitants are in coastal regions. During the last 100 years the sea level has risen about 18 cm (1-2.5mm per year). In another 100 years it is estimated that the rise will be an additional half metre or more.
(At the recent -January 1999- McMurdo Sound ministerial meeting of Antarctic scientists, Tim Naish from the New Zealand Geological and Nuclear Science Institute was reported as predicting that global warming could raise sea levels by as much as six metres in the next generation! Hyperbole indeed!)
If any of these estimates have any validity then the populations of places like the Maldives, Samoa, Marshall Islands, Kiribati, Tonga, and Vanuatu are justified in being extremely anxious as they can bid farewell to their ground water supplies and to most of their land. The dilemma is obviously whether to spend huge amounts of money building the equivalent of Dutch dykes around every atoll or to plan long term migration to higher ground in other countries.
Options of this sort will not be available for instance, for the heavily populated delta communities of Bangladesh and Egypt. I did however, listen to someone at the Second World Climate Conference seriously proposing closing off the mouth of the Mediterranean Sea at the Straits of Gibraltar to prevent any rise in the Atlantic affecting the sea level at the mouth of the Nile!
Prevention in terms of stopping global warming seems to be the only answer – but can it be done?
Vector Borne Diseases
To me, the effect of climate change on the distribution of vector borne diseases is the most intriguing of all. It appears that various insect species, mosquitoes in particular but also a number of flies and bugs which act as intermediary vectors for some of the most rampant infectious diseases, may be extraordinarily sensitive to relatively small variations in temperature, precipitation and humidity. Monitoring mosquito populations may be one of the most important ways of predicting climate change and potential threats to human health.
Fossil records from as long ago as 15,000 years indicate that there have been shifts in insect populations across latitudes that correlate with fluctuations in minimum temperatures as determined from ice core sampling.
At the present time, most vector borne diseases are distributed well within the climatic limits of their vectors. However there are additional factors such as land clearing, the movement of peoples into bush and jungle areas, and increasing irrigation, which are influencing the breeding habits of the vectors and bringing humans into closer proximity to them. Relaxation in anti vector measures has also contributed to the resurgence of vector populations and vector borne disease in many countries.
I don’t intend to discuss all of these fascinating diseases but it is worth looking at several of them that are of particular interest to Australia and our region.
Let us start with Malaria, which now poses the single greatest threat from infectious disease in the world. 2,200 million people in 100 countries are at risk of malaria and of these 300-500 million people are infected each year giving rise to an annual death rate (1997) of 1.5-2.7 million. In addition to the burden of death, the disease itself affects children and pregnant women disproportionately and also has a severe economic impact on affected countries.
This is an international calamity, particularly since WHO in the 1960s and 70s was making great strides towards eradicating malaria world wide. Pesticide resistance on the part of the Anopheline mosquitoes, and drug resistance on the part of the plasmodium parasites were the main reasons that the eradication campaign failed, but the failure of health authorities to keep their eye on the ball may also have contributed. But that is another story.
The new Director General of WHO Dr Brundtland has just launched a major initiative “Roll Back Malaria” in an attempt to regain control over this awful disease concentrating first on Africa where the problem is most acute.
The anopheles mosquito has seen most of the planet over the centuries. As late as the 19th century malaria was endemic in Northern Europe and North America. Australia was declared malaria free only as recently as 1974 and as the mosquito is still found in Northern Australia, it is theoretically possible for the disease to be reintroduced. It remains a serious problem in PNG, the Solomons, Vietnam, Cambodia and Laos in the WHO region of which Australia is a member.
The reasons for the disappearance of both anopheles mosquitoes and malaria from the higher latitudes in Europe and America was undoubtedly due to measures taken to control the breeding of mosquitoes rather than any climate change in the direction of cooler temperatures.
There is now clear evidence that malaria is responsive to local climate change and perturbations. For instance a period of record high temperatures and rainfall in Rwanda in 1987 resulted in an increase of 337 per cent in malaria incidence over the previous three years. The increase was greatest among groups with little acquired immunity – children under 2 years of age and people in high altitude areas. The researchers concluded that temperatures (particularly mean minimum) predicted incidence at high altitudes where malaria had increased most.
To quote the authors: “The patterns of climatic warming between day and night and among seasons will be critical to the effect on malaria. These findings are most relevant to regions near the altitude and latitude limits of the disease.”
Other observations reported in the 1993 series in the Lancet on health and climate change, include outbreaks of malaria in Ecuador, Peru and Bolivia related to heavy rains accompanying the 1983 El Nino Southern Oscillation (ENSO) event. Epidemic malaria will occur then in susceptible populations at the fringes of climatic factors that limit the distribution of the disease.
The anopheles mosquito comes in a number of species and some are able to survive in sheltered places during cold spells. However most anopheles activity comes to a halt when the temperature drops below 22 degrees C, and some species that transmit the deadly falciparum malaria do not survive when mean winter temperature drops below 16-18 degrees C.
While it might be concluded from these findings that warming could be anticipated to increase the possibility of malaria transmission in temperate zones, it seems that this is not necessarily the case unless increased temperatures are accompanied by increased relative humidity. Rain plus warmth are needed for optimum mosquito reproduction. Drought plus heat should actually reduce malaria transmission. In addition, the plasmodium parasite itself is sensitive to temperature and will not develop outside the 14 – 38 degree C range.
WHO’s “Role back Malaria” campaign will need to pay attention to the vulnerable less immune populations at the climatic borders in the face of possible global warming. Bed nets, repellents, effective insecticidal strategies and rapid and effective diagnosis and treatment of cases of malaria – plus national support and commitment - will be the mainstays of the program. These need to be implemented urgently.
The second of these vector borne diseases I would like to discuss is dengue.
Dengue is a viral disease carried by Aedes mosquitoes, notably Ae aegypti and Ae albopictus. (These mosquitoes are also vectors for yellow fever in South America and Africa where monkeys act as reservoirs.)
WHO estimates that 2,500 – 3000 million people in over 100 countries are at risk of both dengue, and dengue haemorrhagic fever - a serious and often fatal variant of the disease resulting from a second infection by another of the four strains of the virus. Deaths number 20 –30,000 per annum but there are millions of clinical cases, and speaking as from the experience of having had dengue years ago in Sri Lanka I can vouch for it being something to be avoided!
There is currently no vaccine against the disease, so any global control strategy has to depend on surveillance of vector densities and disease transmission, vector control including emergency measures in times of acute outbreaks, and good management of patients – particularly those with haemorrhagic manifestations.
The main vector Aedes aegypti breeds in containers (old cans, jars, water containers and old tyres) around human habitations but this is restricted to areas with a mean midwinter temperature exceeding 10 degrees C. Colder temperatures kill both larvae and adults. At present this limits its breeding to south of 35 degrees latitude in North America and in Australia to North Queensland.
Dengue virus has been circulating in North Queensland since 1981 and in the last few years the Tropical Public Health Unit in Cairns has been kept busy dealing with outbreaks of dengue in North Queensland resulting from the arrival of infected persons from Asia and PNG. In one outbreak in Cairns there were three local cases between March and May, while another in the Torres Strait resulted in over 200 cases over the seven month period October to May.
Intensive campaigns have been conducted to ensure that breeding opportunities for mosquitoes are kept to an absolute minimum, and that the population takes steps to avoid being bitten. The Queensland Government takes the matter very seriously as dengue poses a real threat to the tourism industry!
Dengue has spread dramatically from its original origins in Asia in the last 20 years to involve the entire tropical world.
It appeared for the first time in the Caribbean in 1977, coinciding as it happened with a meeting of the International Epidemiological Association in Puerto Rico that I attended. There was I’m sure no cause and effect mechanism operating but everyone at the meeting immediately gave blood in the interest of science to determine the incidence of subclinical infection! There has been subsequent spread to Mexico and South America. All four serotypes of the virus are now found in Africa.
Epidemics can occur wherever vectors are present and where virus is introduced. “ProMED” – the excellent web site that gives daily updates on communicable diseases around the world - is currently (January 1999) reporting a very severe epidemic in Venezuela where the state of Zulia has declared a state of emergency. In 1998 the country had 33,654 cases with 43 deaths.
Has there been a climatic element to all of this? Data to answer this question are not yet conclusive although McMichael and others state that it “seems likely that climate change would effect the distribution, life cycle and population dynamics of this vector.”
The Malaysian health authorities reported 27,370 cases last year – a 42 per cent increase over the previous year. They attributed the rise not to wetter conditions but to the drought that forced people to store water in all types of open containers, thus facilitating mosquito breeding.
In Colombia, Ae aegypti has been discovered at elevations above 2,200 metres where previously temperature had limited it to 1,500 metres. In Mexico too, the mosquito seems to have moved to higher altitudes. Temperature is a key predictor of dengue infection and laboratory experiments have demonstrated that mosquito larval development is accelerated under warmer conditions.
Two years ago, the journal “Emerging Infectious Diseases” reported the re emergence of Ae aegypti in Arizona, noting too that it is now established in the southern states of the USA from Texas to South Carolina and even in Maryland and New Jersey. In late 1997, Ae albopictus (introduced into the USA in used tyres from Asia) was picked up in Illinois! These developments are indeed worrying, particularly as the associated haemorrhagic and shock syndromes are becoming more common as clinical manifestations.
Again, as for malaria, mosquito monitoring and control will be essential and public health authorities should be aware that these vectors are tending to move towards more temperate climes and take appropriate action.
The third and last of this group of vector borne diseases that warrants our attention in Australia is Japanese Encephalitis.
When in 1995 I received a call from the Chief Health Officer in Queensland to say that there had been three cases of Japanese Encephalitis on Badu Island in the Torres Strait, my initial reaction was of disbelief. We hadn’t had an outbreak of Australian Encephalitis (Murray Valley Encephalitis) in Australia since 1974 and we had perhaps become a little too confident that outbreaks of life threatening viral encephalitis were things of he past.
Also everyone believed that Japanese Encephalitis was not something that would ever affect Australia as it had traditionally been limited to Asia and had never been seen east of Bali, some 3000 kilometres from the Torres Strait.
Once the diagnosis was confirmed I had to make special urgent arrangements through friends in the Japanese Ministry of Health in Tokyo to expedite the importation of the vaccine. (In 1998 a case was diagnosed on the Australian mainland in North Queensland for the first time in history.) The big question remained - why did it happen? Is this another example of what might happen under climate change?
Neville Nicholls of the Bureau of Meteorology Research Centre in his 1993 Lancet paper “El Nino Southern Oscillation and Vector Borne Disease” had warned that extended heavy rainfall often preceded outbreaks of vector borne diseases. He cited the 1988 epidemic of JE in Uttar Pradesh which killed 5000 people, most of them children.
This does not seem to have been the scenario for the Badu Island outbreak. John McKenzie from the University of Queensland has shown that there is serological evidence that JE had – unknown to PNG health authorities - actually become enzootic in PNG over a period of up to 15 years or so. In other words the cycle between the vector culex mosquitoes and animal reservoirs, notably wild and domestic pigs, has been going on in a steady easterly progression from Indonesia to PNG and now to Australia. Entrance to the Torres Strait and North Queensland was most likely through windblown infected mosquitoes.
(On 21 January 1999 ProMED announced that an Australian mosquito species Ae camptorhynchus – known to carry Ross River virus – had been found for the first time ever in the Napier district of New Zealand. Is this another example of windblown mosquito movement perhaps?)
Are the winds changing?
Japanese Encephalitis has a high case fatality rate and is so serious that in Taiwan all children are immunised every year. Six hundred people died in Cambodia last year and in January 1999, Malaysia reported 14 deaths mainly in young people engaged in pig farming. JE is seasonal in Malaysia occurring during the months of November to January, a time of higher than usual precipitation.
In Australia vaccine is now available to the communities at risk and steps have been taken to reduce mosquito breeding around pig farms in the Torres Strait. What requires further elucidation is the effect of ENSO and wind patterns on the breeding and distribution of the vectors.
Other Infectious Diseases
Time will not permit consideration of a number of relatively common food and water borne diseases whose incidence increases in times of catastrophic events (eg typhoid or hepatitis A after floods), or general warming in the absence of refrigeration and proper food handling (salmonella, E.coli, campylobacter etc).
Previously rare diseases make their appearance at times of climatic stress. In January this year Chile reported the deaths of 4 people from hantavirus pulmonary syndrome which results from inhaling or ingesting rat faeces. During the current drought, rats have been coming into closer than usual contact with human populations as they seek food.
Leptospirosis – spread by rat urine - is also becoming more apparent in some countries and can be exacerbated by floods.
The really interesting disease worth considering for a few minutes is cholera. Cholera is caused by the bacillus Vibrio cholerae and has a faecal –oral mode of spread. It has been known and feared for centuries and has probably been endemic in the Bengal region of India since the late 15th century.
The world wide spread of cholera started in 1817 and during the nineteenth century there were five pandemics of cholera spreading along the trade routes from India to Europe, Africa and North America. The sixth pandemic from 1902 to 1923 was mainly centred in Asia as was the seventh that started in Sulawesi 1961 and lasted through to the1980s. The eighth started to invade sub Saharan Africa in 1970 and then spread to South America in the early 1990s with disastrous consequences. A new and more virulent strain is now spreading westwards from South East Asia into the margins of Eastern Europe.
WHO in 1997, reporting on the previous year, noted a decrease in overall numbers with a total of 143,349 cases and 6,689 deaths being reported from 71 countries.
In the region of the Americas, the number of cholera cases dropped from 85,809 the previous year to 24,643. This lead WHO to comment: “As the epidemic enters its seventh year in the Americas, cholera still serves as a reminder of deficiencies in water quality, sanitation and hygiene, that will continue to challenge governments and health agencies into the next century.”
The origin of the South American epidemic (the first ever in that part of the world) is fascinating. Paul Epstein has described it well: “ At the end of January 1991 an outbreak of acute diarrhoea was reported in the city of Chancay, 60 km north of Lima. A day later the same occurred in Chimbote a seaport 400 km north of Chancay, and on 31 January cholera was confirmed with 12,000 cases reported over the next 2 weeks. Moving with unexpected speed and intensity the epidemic spread 2000 km along the Peruvian coast and into Equador. On 8 March, Colombia and on 16 April, Chile, reported cholera in port cities 800 km and 1700 km respectively from the previous epicentres, and by April of 1992 a total of 533,000 cases and 4700 deaths were reported from 19 nations in Latin America.”
In December 1991 cholera vibrios of a specific biotype and serotype were isolated in marine and fresh water, in sewerage lagoons, and in samples of marine and fresh water plankton near Lima, Peru. The aetiologic agent in over 99 per cent of the cases has been this specific vibrio. The identical organism was recovered from the ballast, bilge, and sewerage of three ships docked in the Gulf of Mexico; the previous ports of call having been in Brazil, Colombia and Chile. The assumption was that the dumping of bilge and sewage into the sea off the South American ports had contaminated the fishing catches used to prepare a popular dish made from raw fish.
The persistence of the organism in the water gave further support to the long held hypothesis of an environmental reservoir for V.cholerae. For instance it has been well documented that peak incidences of cholera in Bangladesh occurred together with the bloom of cyanobacteria.
Evidence is now accumulating that marine phytoplankton provides a refuge for the dormant spore-like vibrio that shelters beneath the mucilaginous sheath of algae. When adverse conditions due to shifts in pH, temperature, salinity and nutrients occur, the vibrios contract and “hibernate”. When waters warm the cholera organism re-emerges in an infectious state.
To quote McMichael et al: “The spread of cholera may thus be influenced fundamentally by levels of marine eutrophication (caused by discharge of urban effluents consisting of high levels of pollutants) and increased sea surface temperatures (a climatic factor) both of which promote the growth of phytoplankton populations. In other words, human- induced and natural disturbances of coastal ecosystems play an important role in cholera transmission.”
With global warming we may well have increasing difficulties in containing cholera.
While I know that the question of ozone depletion in the stratosphere is not one that fits in with the topic of “Weather, Climate and Health ”, there are health implications especially for Australians with pink skins. There is also an important lesson to be learned from this subtopic regarding the way the public is informed about health hazards from ultraviolet radiation.
Australia continues to be at the top of the world melanoma and non melanoma skin cancer charts with an incidence in males of 40.1 and 1,187 cases per 100,000 population respectively. It is hoped that this will change as the younger generation avoids blistering sunburn and follows the “slip, slop, slap” advice put out by health authorities. It is evidently too late for those of us in the older generation with already damaged skins.
The evening news now gives us all the ultraviolet readings for the day – an initiative started by the Australian Radiation Laboratory some years ago – and a better informed population alters is behaviour accordingly one would hope.
In relation to the “hole in the ozone layer” the messages given by the media and meteorologists it would seem are less consistent and therefore confusing. Confusion is not something the public can handle well. If we – the scientific community are not sure whether the hole is increasing or decreasing in size then maybe it is better to say nothing until we are sure!
While the nation is no doubt meeting its international obligations under the Montreal Protocol, we need more certainty as to whether the problem is getting better or worse.
Conclusions
What conclusions can we draw from the sorts of evidence we have been discussing? The main one I suppose is that while there are some fascinating hypotheses about the changing natural histories of a whole range of conditions there is still a great amount of scientific uncertainty. All the publications that attempt to summarise the level of current knowledge on climate and health – including the excellent publication of the Inter Governmental Panel on Climate Change “Climate Change 1995” – are full of “ifs” and “maybes”.
Take the following quote for example: “Climate changes and their effects on food security, water supply and quality, and the distribution of ecological systems may have wide-ranging and potentially adverse effects on human health, via both direct and indirect pathways; it is likely that the indirect impacts would, in the long term predominate. Quantifying the potential health impacts of climate change remains difficult. For many effects, forecasting techniques- especially modelling- are just being developed. Furthermore the extent of climate- induced heath disorders depends on numerous coexistent and interacting factors that characterize the vulnerability of the particular population. These include environmental circumstances (such as water purity) and socioeconomic factors (such as nutritional and immune status, population density and access to medical care).”
While these uncertainties are being resolved over the next decade or so it is important to continue taking public health action where such action is known to be effective in controlling or eliminating health problems. It is also important to identify vulnerable populations who should be given first priority for implementation of such action.
What should government be doing? At the national level the time is ripe for greater research activity to help elucidate more precisely the links between human health, weather and climate. The National Public Health Partnership has recently put out a discussion paper “Environmental Health in Australia – Towards a National Strategy” which calls for action to improve the monitoring of vector borne disease in the light of climate change. The discussion paper is regrettably silent on other aspects of climate and health but now is the time for it to be strengthened and any omissions corrected.
The NHMRC has just undergone an extensive review of its health and medical research activities (the Wills review). The resulting discussion document, entitled “The Virtuous Cycle – Working Together for Health and Medical Research”, released in December 1998, should encourage researchers interested in climate and health to write in urging the NHMRC to embrace this field as a legitimate one for research funding. Such research will of necessity have to be multi disciplinary in nature.
The National Greenhouse Strategy released in 1998 calls for investigation of the potential climate change impacts on human health, calling for more research on vector borne diseases and calling for the development of a framework which would include:
(a) assessing the need for increased public health and control programs
(b) improving ecosystem or agriculture management to reduce the potential for invasion by vectors
(c) developing and introducing protective technologies
(d) improving primary health care of vulnerable populations (eg indigenous, young and aged groups, or regionally)
(e) education campaigns to change high risk behaviour (eg encouraging widespread use of insect resistant netting and clothing).
At the international level there has been much activity since 1986 when the World Meteorological Organization (WMO), World Health Organization, and the United Nations Environment Program (UNEP) first met to review the relationship between climate and human health. Twelve years later, the resulting collaborative program on climate and health - formulated by the three bodies - was approved by the Inter Agency Committee for the Climate Agenda.
The newly formed “cluster” on Sustainable Development and Healthy Environments at WHO Head Office will have major carriage of this program. We can but hope that it will receive the necessary resources to allow it to stimulate research, disseminate the latest information, and to assist member states – particularly those most vulnerable at this point in time.
The theme for this 1999 World Meteorological Day is a fascinating and vital one, and all of us will be affected one way or another by whatever happens to our global climate. WHO and WMO will need to continue their vitally important collaboration for many decades to come.
Do we all face disaster or – as Gary Taubes wrote in Science in November 1997 in his article “Apocalypse Not”- is the whole issue is merely a beat up by a few over -enthusiastic epidemiologists? Whatever the answer, we are duty bound to improve our monitoring and research activities, and we are obligated to augment public health measures designed to respond to the threat of epidemic disease and man made disasters.
Our national and international public demands no less of us.
Ends
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