Fowl play

January 3, and all is not well in Hong Kong. With four people dead, and 11 confirmed and six suspected cases of A (H5N1) infection, the new strain of influenza virus, transmitted to humans from poultry, has wrecked havoc in Hong Kong. The latest in a series of knee-jerk reactions is the mass slaughter of all poultry, especially chicken

Published: Saturday 31 January 1998

Fowl play

Chicken-scared: caged chickens (Credit: Photographs: AP / PTI)on december 29, 1997, Hong Kong's administration started slaughtering all poultry in the region in an effort to stop the spread of the new strain of influenza virus, a (h5n 1). By January 3, 1998, several unanswered questions remained scattered amidst the rotting carcasses of more than a million birds. Questions regarding the spread of the virus in humans, the possibility of an epidemic, the effectiveness of mass slaughter of poultry in the region and its consequences.

The mass culling of poultry has drawn flak from various quarters, particularly on the cost of the exercise and the way it was carried out. The operation was conducted by personnel from seven governmental departments. After being disinfected, carcasses were wrapped in plastic bags and buried in landfills. Although the government had claimed that the entire operation would be over in a day, five days after it started, health workers were still left with about 68 tonnes of dead meat. Officials admitted that the cull had been conducted shabbily. Lessie Wei Chui Kit-Yee, director of agriculture and fisheries, and the chief official behind the mass slaughter, offered to resign on January 1 after thousands of birds escaped the cull and many carcasses could not be disposed of. "I am not finding excuses. Our records showed that there were 161 chicken farms. But 68 new farms were discovered during the operation," she said.

Buddhist and Taoist leaders in Hong Kong declared that they would perform religious rites for the more than 1.2 million chickens that were slaughtered. Reverend Yong Xing was reported to have said that the rites were to "appease" the dead chickens because "mass slaughter of animals is an unlucky omen".

Though this had little to do with the spread of the disease, the panic in Hong Kong following the death of four people infected with a (h5n 1) bodes ill and has the portents of a global health disaster. Although a greater part of the population remains unaffected, the avian flu, as it has been called in the media, is causing unprecedented concern in medical circles. It touches on an aspect of day-to-day existence, the consumption of meat and poultry.
Strange turn The outbreak of a (h5n 1) infections appeared harmless in the beginning. In April 1997, infected chicken at the Yeun Long farm in Hong Kong began ignoring food, slumped listlessly, and died in a few days. The infection then spread rapidly and killed entire poultry populations in some farms. On May 11, 1997, a three-year-old boy, whose name remains undisclosed, fell ill. He was admitted to the Queen Elizabeth Hospital on May 15 with symptoms of severe pneumonia and Reye's syndrome. Characterised by inflammation of the brain, Reye's syndrome occasionally affects children who have been exposed to a flu or chickenpox virus. The boy died 10 days later.

For three months, health authorities failed to identify the cause of his death despite an autopsy. Margaret Chan Fung, Hong Kong's director of health, sent cultures of the virus obtained after a throat biopsy to three international laboratories, including the Center for Disease Control (cdc) in Atlanta, Georgia, usa's premier medical research facility. The agriculture and fisheries department of Hong Kong had also sent samples of infected poultry to another laboratory in the us that ascertained the presence of a (h5n 1).

Researchers at the Atlanta laboratories, after exhausting all possibilities of infection by viruses known to infect humans, found that the samples matched the influenza virus strain that infects birds, pigs and horses. On August 18, cdc confirmed the presence of a (h5n 1) in the viral cultures. This was the first confirmed case of a (h5n 1) infection in a human being. "There is no indication at present that this strain has spread from person to person. There is, consequently, no need for special measures as of today," Daniel Lavanchy of the World Health Organization's (who's) division of emerging and other communicable diseases' surveillance and control at Geneva was reported to have said, following the report from cdc (Down To Earth , Vol 6, No 12).

However, on December 6, a 54-year-old man became the second victim of a (h5n 1) when he died of viral pneumonia. This was followed by the death of a 13-year-old girl and a 60-year-old Filipino woman. In the third and fourth weeks of December, more cases started coming to light, and sent alarm bells ringing across Southeast Asia. The Malaysian government declared that it was keeping a close watch on the situation. The province of Sabah in Malaysia imposed a total ban on the import of livestock, poultry and related products from Hong Kong. The "outbreak" could not have occurred at a more importune time than Christmas for thousands of small-scale traders. Chicken -- favoured in various food preparations around this time of the year -- disappeared from restaurant menus and stalls.

When the administration, in the highly publicised reaction to the outbreak, decided to slaughter all poultry in the region, the suffering had spread beyond the victims and the poultry industry. Hong Kong had been reeling under the pressure of an economic crisis that gripped Southeast Asia, following the spread of smog from forest fires in Indonesia. Although who did not issue any guidelines or directives regarding quarantine measures, Hong Kong's reputation suffered. Tourism, an important source of income for Hong Kong, declined further. By January 3, the count of those infected with a (h5n 1) rose to 15, and four people had died. Six more were suspected to be infected, but authorities were awaiting confirmation.

Dj vu: Flu epidemics in Hong Kong
What has made fears regarding the present outbreak in Hong Kong worse are memories of previous flu epidemics. Just after World War i (1918-19), there was an outbreak of "Spanish flu". About 200 million people were infected, and 20 to 40 million died. In 1957, what came to be known as Asian flu claimed about 98,000 lives, primarily in Hong Kong. Yet another flu epidemic killed 46,000 people in Hong Kong in 1968. Medical experts are trying to assess whether the present outbreak can blow into another influenza epidemic.

Influenza viruses that cause illness in humans are of two groups, a and b . That the culprit in the present outbreak in Hong Kong has been identified to be the influenza " a " virus is a consolation. This means that it can be treated with the drug amantadine, which kills influenza a viruses if the victim receives medication before the infection reaches advanced stage, but is ineffective against influenza b viruses. Virologists further label each strain of influenza virus by its specific proteins -- haemagglutinin (h) and neuramidase (n). Following monitoring and investigation by health authorities in Hong Kong and at the cdc , it has been established that the virus is a new type of influenza. It has been described as an influenza a (h5n 1) strain because it has specific antigens that can react with the immune system.

Another known aspect of the virus is its ability for rapid genetic mutations. "If it is a minor change, the general population will have immunity from previous infections. But if it is a shift, you are almost dealing with a new virus," said Paul Saw Thian, Hong Kong's deputy director of health. It is of no mean importance that this new virus has an h 5 antigen. This is a tiny spike, visible only with an electron microscope. Each time the flu virus evolves into a killer, it undergoes what the virologists call an "antigenic shift", changing the " h " factor (which affects blood cells) into something that the human immune system cannot easily recognise and destroy.

By evolving a new agglutinin, the influenza virus effectively buys enough time to mount an overwhelming attack on the respiratory tracts before the immune defences can develop the right antibodies to neutralise the new strain.

The influenza virus that killed more than 20 million people during the 1918-19 pandemic of Spanish flu had an h agglutinin named h 1 by virologists. The next big killer, the Asian flu that again killed about a million in 1957, had changed its h agglutinin to what was labelled h 2. And in 1968, when the "Hong Kong flu" swept the world and activity at schools, businesses and other establishments ground to a halt, with thousands affected by the new strain, the virus was found to have an h 3 agglutinin. The toll was significantly low in 1968 because the other significant feature -- the " n " antigen -- was the same as the one found in the virus responsible for the 1957 pandemic. Although no one had exactly the right antibodies to fight off the virus in 1968, many people had antibodies to give them a chance of fighting the virus.

The avian flu virus found in Hong Kong has a new " h " agglutinin, now identified as h 5. This implies that should it change its genes enough to be able to spread from humans to humans, it could evolve into a strain that can kill on a massive scale.

The mode of transmission in the present situation remains enigmatic. Medical experts have been arguing for the last few months that the virus is not easily transmitted. They point to the fact that most of the cases of a (h5n 1) infection ensued from contact with poultry, meaning that the virus could not spread from person to person. But on December 26, health workers reported the first evidence of probable human-to-human transmission of a (h5n 1).

The transmission was detected from blood tests in a doctor who had attended the three-year-old boy who died in May. But the physician did not remember developing any symptoms of the respiratory ailment at the time and continued to be in good health, suggesting that people can be infected without showing symptoms in the early stage of infection. Health officials suspect that the physician received the infection by touching the child during treatment, and not through the air. For reasons scientists do not understand, the virus was not transmitted to others.

A disaster waiting to happen?
When it comes to finding out how the virus can become a killer on such a large scale, Hong Kong has something to boast about. Kennedy Shortridge, professor of microbiology at University of Hong Kong, has been conducting research on this aspect since the 1970s. His team has shown that the flu virus is only meant to stay in birds as a 'bowel virus.' Such viruses are found in ducks, chickens and wild, migratory birds but are not known to infect humans. They lack the right immune locators (antigens) needed to lock on to receptors in human throat cells and blast their way into the respiratory tract, causing the sore throat, fever, cough and bronchitis familiar to anyone who has had influenza.

The virus is released into the environment through droppings from infected birds. These are often eaten by pigs, especially in southern China's crowded farmyards. It has to be noted that three-fourths of all chickens in Hong Kong are imported from this region. As pigs have receptors that are the similar to human receptors, along with receptors similar to those found in the cells of birds, pigs can get both human and avian flu strains. Shortridge points out that the pig is like a mixing vessel, allowing the avian virus to reinvent itself just enough to become a new human virus -- different enough to outwit our immune systems. Shortridge, in association with the department of agriculture and fisheries, is now sampling pigs, chickens, dogs and cats to see if the virus is undergoing genetic mutations large enough to cause a human pandemic.

When the three-year-old died in May, investigators concluded that the case was isolated. But with at least 15 confirmed cases now, experts are considering the possibility that the virus has become clever enough to skip the pig stage and go straight from birds to humans. This raises a question: Can the virus attack entire human populations or just the people with the immunological make-up to receive it?

Shortridge's studies in southern China suggest that some farmers there get the avian flu but do not even know it. The people at risk of getting the disease and the doctors treating them need to find out the kind of flu they have and what they can do about it. The best protection against the virus will be vaccination. who and cdc are working in tandem to develop a vaccine against a (h5n 1). However, it will take time to develop. And people in Hong Kong are at the mercy of the virus till there is a breakthrough.

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