Think chickens and pigs, bats and ticks. As new virus vectors emerge, Asian governments are pinning their hopes on a novel option. Luck.
By THOMAS ABRAHAM
Hong Kong, February 2011
The calm before the cull: An Indonesian health worker carefully inspects chickens at a farm. - Photo: Getty Images
IN THE autumn of 1998, workers on pig farms near the town of Ipoh in Malaysia began to fall ill with a strange disease. They developed fever, splitting headaches and felt disoriented and confused. Some went into a coma and died. The local health authorities assumed it was Japanese encephalitis, a disease that is transmitted from pigs to humans through mosquitoes, and sprayed areas around the farms with insecticide.
This did not help, and the disease spread to the Bukit Pelandung area in the nearby state of Negiri Sembilan, the heart of the Malaysian pig industry and home to over a million pigs raised on farms owned by the country’s ethnic Chinese minority. As increasing numbers of farm owners and workers began to fall ill and die, other farmers fled their farms, either selling their animals for whatever price they could get, or abandoning them. The army was sent in to help slaughter abandoned and diseased pigs. Political tensions rose as opposition politicians criticised the authorities for being unable to stop the disease and demanded more compensation for the affected farmers.
The culling of over a million pigs in Malaysia finally stamped out the outbreak, but not before at least 265 people had been infected, forty percent of whom died. The Malaysian pig industry, one of Southeast Asia’s largest, had been destroyed by culling and public fears about the safety of pork. Pigs exported from Malaysia had carried the disease to Singapore, causing one death and several cases of illness among abattoir workers.
The culling of over a million pigs in Malaysia finally stamped out the outbreak, but not before at least 265 people had been infected, forty percent of whom died. The Malaysian pig industry, one of Southeast Asia’s largest, had been destroyed by culling and public fears about the safety of pork
It became apparent that the disease was not Japanese encephalitis. The cause of this disaster was eventually traced to a previously unknown virus, the Nipah virus. The Nipah virus is normally found in large bats, such as the Malaysia flying fox. Flying foxes had been noticed in the fruit trees surrounding many of the pig farms. The pigs were probably infected after eating fallen fruit the bats had nibbled on, before passing the virus on to humans.
Nipah is only one of the latest of a series of previously unknown infectious diseases that have emerged from animals to infect human society. SARS is the most powerful recent example, while HIV/AIDS is probably been the most significant in public health terms. CCHF (Crimean-Congo haemorrhagic fever), a tick-borne viral disease that has was first recorded as early as 1944, was reported in January 2011 in Gujarat, India.
As human populations alter the environment, and encroach into new ecosystems, the risks of such diseases emerging increases. The arrival of Nipah is a classic example of the complex ways in which human activity can lead to new outbreaks. The large flying foxes that settled in the fruit trees around the pig farms in Malaysia are normally forest dwellers, rarely seen around human habitation. What drove them so close to human beings? The arrival of the flying foxes were preceded the previous year by the heavy haze caused by forest fires in Borneo. The haze, which had spread as far as Malaysia and Singapore, it is hypothesized, prevented trees in the forests from fruiting, and drove the bats from their traditional habitats closer towards human habitation.
Nipah has never re-appeared in Southeast Asia, having disappeared as mysteriously as it appeared. But it did turn up three years later and several thousand miles away in Bangladesh. In April and May 2001, an outbreak of a mysterious illness, which caused high fever and headaches leading to a coma and death were reported from villages in Meherpur district in southwestern Bangladesh, an area of jute and tobacco farms and mango and lychee orchards. Laboratory and epidemiological analysis showed that Nipah had struck again. Unlike in Malaysia, there were no pigs around, so the disease probably passed directly from bats to humans.
Since then, there have been several outbreaks reported in Bangladesh, as well as in the neighbouring Indian state of West Bengal. Each outbreak has provided evidence that the virus has the ability to transmit from human to human (and not merely from animal to human). In Siliguri in West Bengal, Nipah demonstrated its potential for destruction by transmitting rapidly within a hospital after a patient infected staff and visitors in a grim multiplier. Like most viral diseases, there are no effective anti-viral drugs, and fatality rates are high: in Bangladesh and India, over 60 percent of those who were infected died.
Nipah, SARS and the H5N1 avian influenza outbreaks which have occurred since 2003 show how vulnerable Asia is to outbreaks from newly emerging infectious diseases. The SARS corona virus passed from bats to civet cats through a mechanism that is still not understood, and from civet cats to humans, through workers in the markets in southern China where the civets were sold. More recently, in the Philippines a virus that is a distant cousin of the ebola virus managed to infect pigs and humans. The ebola reston virus was known only to infect monkeys, but in 2008 the virus was found to have infected and caused disease among pigs in the Philippines. Blood tests revealed that farm workers had also been infected by the pigs, though they showed no sign of disease. It is not hard to foresee a situation where similar viruses would emerge to cause serious outbreaks.
Globalisation has meant that outbreaks in one country can spill rapidly to neighbouring regions. Given the speed of modern air travel, a sick passenger can carry a virus from Asia to Europe in a matter of 12 hours, and from Asia to the United States in around 18 hours. Within Asia, diseases can travel even quicker, carried either by human beings or livestock crossing borders. So what mechanisms do we have to prevent the spread of new diseases?
Post SARS, on paper at least, procedures for the early detection and control of new diseases exist. SARS spread initially because China covered up the existence of the disease for several months. It spread globally after a sick doctor from China who was staying in a Hong Kong hotel, infected fellow guests who in a matter of hours took the disease with them to Vietnam, Singapore and Toronto, creating a global outbreak. Since then, huge efforts have been made at the international and regional level to put in place systems to detect new diseases quickly, and prevent them from crossing national boundaries.
The International Health Regulations, a legal treaty that is administered by the World Health Organisation, now requires countries to report disease outbreaks that could cross international borders to the WHO. It also requires countries to develop the capacity to detect and respond to disease outbreaks.
The fact of the matter is, that were a SARS-like disease to erupt again, there is little guarantee it will be caught and controlled before is crosses borders. A major hurdle is knee-jerk governmental secrecy. As with SARS in China, governments are often reluctant to admit they are facing an unknown disease
But the fact of the matter is, that if a SARS-like disease was to erupt again in the region, there is little guarantee that it will be caught and controlled before it crosses borders. One big hurdle is governmental secrecy. As in the case of SARS in China, governments are more often than not reluctant to admit they are facing an unknown infectious disease. Fears of the economic impact this might have through reduced international trade and falling tourist arrivals as well as worries about public panic tend to lead governments towards knee-jerk cover-up in the hope that the issues will go away. Unfortunately, nothing aids the spread of disease more than secrecy: neighbouring regions and countries cannot respond or prevent diseases from crossing porous borders if they are unaware that a threat exists.
Even if governments did want to detect and respond speedily to new diseases, the capacity to do so in Asia is limited. While the more developed economies like Japan, Korea and Singapore have the capacity to detect and respond to diseases rapidly, others do not. Countries like Laos, Cambodia and Myanmar, to take three examples do not have the resources to create sophisticated disease surveillance and response systems.
Catching a new infectious disease early requires a number of things: disease reporting systems in cities, towns and villages that are sensitive enough to pick up unusual distress signals. These systems could be as simple as a large number of flu cases occurring outside the normal flu season, or a dogged illness that does not seem to respond to normal treatment. This surveillance system needs to be matched with a communication system that allows this information to flow from villages and remote rural areas to the Ministry of Health so that those in charge of a country’s health system are aware of what is happening. The surveillance system also needs to be backed up by reasonably well equipped laboratories capable of testing samples.
All of this is in short supply. The one infectious disease threat that countries in the region have some capacity to detect and respond to is H5N1 avian influenza. Because of the worries in the United States and the developed world that the H5N1 virus could cause a pandemic, resources were pumped into helping countries in Asia to detect and respond to H5N1 outbreaks rapidly, and hopefully preventing, or delaying it from reaching the rest of the world. That surveillance and response capacity is limited to detecting outbreaks of avian influenza and is concentrated in Indonesia, Thailand and Vietnam, the countries most affected by H5N1. There is little generic surveillance and response capacity to deal with viral threats.
It also complicates matters that these new threats often involve animals that are farmed for food. This leads to inevitable turf battles between ministries for health and agriculture, as well as between human health and animal health specialists. Ministries of agriculture, which are typically in charge of animal husbandry and animal health, are mindful of the commercial consequences of culling livestock, and are reluctant to take aggressive steps against the livestock industry that public health specialists often urge in order to stamp out diseases.
As Asia’s population continues to grow, new stresses will emerge in the relationship between humans, animals and the environment. These stresses will allow new viruses to emerge and cause human infections. If we are lucky, they will peter out after causing small pockets of disease, as has happened in the case of Nipah. If we are slightly less lucky, these diseases will travel a bit farther but die down after disturbing a particular part of Asia, as happened in the case of SARS. If we are really unlucky, a new disease could arise that would have the ability to sweep across continents.
So far, over the past few decades, luck has favoured the region. But luck is no substitute for a well integrated, regional system to speedily detect and respond to infectious disease threats. Unfortunately, thus far, many Asian governments appear to have put their faith in luck.
Thomas Abraham is Director of the Public Health Communication Programme at the Journalism and Media Studies Centre at the University of Hong Kong, and author of Twenty First Century Plague, the Story of SARS. He has specialised in infectious disease risk communication, and worked at the World Health Organization in Geneva in 2009 during the influenza pandemic. Abraham has also served as a consultant to the WHO and other international organisations. In an earlier life he was a journalist for more than 25 years including stints as a foreign correspondent for The Hindu newspaper in India, and as Editor of the South China Morning Post in Hong Kong.
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