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VIRAL EPIDEMIC SHOWS UP THE CRISIS OF NEW DISEASES

It is still not very clear whether the viral epidemic in Malaysia is caused by Japanese encephalitis, or a Hendra-like virus, or something else. This mystery is not peculiar to Malaysia. It is part of the recent outbreaks of new and emerging diseases that are now plaguing the world.

By Martin Khor


April 1999

The tragic viral epidemic that has claimed 95 lives in Malaysia is a scary reminder of the threat posed by new and emerging viruses and bacteria.

It is reported that up to now, 251 people from two states have been infected, out of which 142 have been confirmed to be either Hendra-like or JE cases, or both.

A few years ago, there was also an epidemic of Coxsackie disease which claimed many lives, especially in East Malaysia. It was then also not very clear whether the patients had been hit by the traditionally-known Coxsackie microbe, or a new strain of it, or perhaps another not-yet-discovered ailment.

Even international experts who are helping Malaysia to track down and counter the puzzling diseases have had problems identifying them.

This highlights the problem of new versions of known diseases, caused by new or 'mutant' strains of microbes.

In the past 20 years, at least 30 new diseases have emerged, threatening the health of hundreds of millions, according to the World Health Organisation.

The situation is grave because the new bacteria or viruses spread rapidly, whilst health policy-makers and scientists are still groping to find solutions. As the WHO put it in its 1996 World Health Report: 'For many of these diseases there is no treatment, cure or vaccine and the possibility of preventing or controlling them is limited.'

Probably the best-known new disease is AIDS, which emerged in the late 1970s. The number of HIV cases could grow to 40 million by the year 2000.

A new breed of deadly haemorraghic fevers has also struck in Africa, Asia, the US and Latin America. The most notorious is Ebola, which struck in Zaire in mid-1995. It affected 316 people, of whom 245 died, giving a very high 77% fatality rate.

In the US, the hantavirus pulmonary syndrome was first recognised in 1993. It causes respiratory failure and has a fatality rate of 50%. Cases were also found in Canada, Argentina, Brazil and Paraguay.

Others newly identified were the guanarito virus in 1991 (causing Venezuelan haemorraghic fever) and the sabia virus in 1994 (causing Brazilian haemorraghic fever).

New animal diseases also pose risks to human health through the food chain. These are difficult to evaluate or predict, says the WHO.

The most dramatic example of this is the 'mad cow disease' or BSE (bovine spongiform encephalopathy). Fears have grown that the infectious agent may be passed through the food chain to cause a variant of the incurable CJD (Creutzfeldt-Jakob disease) in humans.

Other new diseases reported by the WHO include the following:

* A completely new strain of cholera, called Vibrio Cholerae 1038, appeared in India in 1992 and has since spread to South-East Asia and western China.

* Several new hepatitis viruses have recently been identified. Hepatitis B has infected two billion people alive today, of whom 350 million are chronically infected and at risk from death from liver disease. Similarly at risk are another 100 million who are chronically and incurably infected by Hepatitis C.

* Epidemics of food-borne and water-borne diseases due to new organisms (such as cryptoporidium) or new strains of bacteria (such as E. coli) have hit rich and poor countries alike.

* The threat of a new global influenza pandemic is increasing. Major shifts in the make-up of influenza viruses occur every 20 years or so, triggering large epidemics and causing thousands of deaths. The next such shift is expected very soon.

Among the causes of the rapid spread of infectious diseases are unhygienic conditions (including lack of water and sanitation) providing breeding grounds for infectious diseases; economic crises that cause a deterioration of public health systems; and the movement of refugees and displaced people which provide breeding grounds for infectious diseases and their spread.

More significantly, for new or emerging diseases, there are also factors such as:

* The rapid increases in air travel, tourism and trade in food which have transported disease-producing organisms rapidly across continents.

* The global food trade creates new opportunities for infections to flourish, such as livestock shipment; food production, storage and marketing; and altered eating habits.

* Environmental change is a major cause. Expanding areas of human habitation put millions at risk from pathogens previously rare or unknown as causes of human disease. The effects of climate change may also give some diseases the opportunity to spread to new areas.

* Antimicrobial drugs have become less effective. Microbes continue to evolve and adapt to their environment, adding antibiotic resistance to their evolutionary pathways.

A critical issue that has emerged is how viruses or bacteria 'mutate' to become new varieties.

It is even more interesting (and probably more frightening) when an existing disease takes on one or more of the characteristics of another disease.

For example, most strains of the E. coli bacterium (which inhabits the gut of humans) are harmless. But some strains such as E. coli 0157: H7 can cause severe disease, including bloody diarrhoea.

This strain of E. coli produces 'Shiga-like' toxins that are similar to the toxins produced by another microbe, Shigella dysenteriae. Many thousands of people, including in Japan, contracted this dangerous variety of E. coli.

According to a microbiology professor in London, who was interviewed on radio in the United Kingdom, there is a possibility that there was a process of 'horizontal gene transfer', in which a gene of the shigella dysenteriae microbe transferred to the E. coli microbe, thereby accounting for a characteristic of shigella being present in the E. coli 0157: H7 strain.

Knowledge of the process of 'horizontal gene transfers' is still emerging. Much more research work needs to be done in this area, if we are to understand the new and emerging diseases more adequately, so that better ways are found to identify and counter them. - Third World Network Features

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About the writer: Martin Khor is Director of the Third World Network.

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