Growing threat of an avian flu pandemic

Flu viruses have been classified into various subtypes depending on certain proteins on the surface of the virus (the hemagglutinin or HA protein and the neuraminidase or the NA protein). Pandemic viruses appear as a result of a process called "antigenic shift," which causes an abrupt major change in Influenza A viruses. These changes are caused by new combinations of the HA and/or NA proteins on the surface of the virus, resulting in a new Influenza A virus subtype which, if it spreads easily from person to person, causes a pandemic.

In 1918 one of human history's most devastating pandemic influenza viruses killed between 50 million to 100 million people worldwide. A new frightening sign is looming on the horizon about the potential of another such pandemic flu spreading from the Asian bird flu and slowly sprawling across national boundaries.

Researchers claim that the 1957 and 1968 global pandemics were caused by human flu viruses that picked up some bird flu components. Test results are indicating that the far more lethal 1918 virus was most likely an avian strain that transmitted directly into humans. This maps two routes for today's avian strain to wreak catastrophic havoc among humans:

• Either through mixing some of its genes with human influenza like the 1957 and 1968 viruses, or
• By self-mutation, becoming easily transmissible among humans following the traits of 1918 virus.

Scientists argue, since conventional flu is highly contagious, a co-infection with the two types of virus may become the most likely route for the bird flu virus to transmit readily from human to human. In the same body -- as in a laboratory -- flu viruses often trade genes, creating new, more deadly pathogens.

Although the 1918 flu was highly contagious, while today's bird flu has so far seemed uninterested (or unable) to spread from person to person, the growing fear is that a mutation making the virus more transmissible could set the stage for a pandemic. Though it does not often infect humans, it can, and when it does, it seems to be ferociously lethal. The frightening report is that the 1918 virus appears to have jumped directly from birds to humans, and that the mutations that allowed it to happen are already in the process in the avian strain, known as H5N1, which has killed 50 percent of those infected (60 out of 116 reported cases).

Another concern is that H5N1 has become so widespread that it killed millions of birds in 11 countries and dispersed further as migratory birds carry it even greater distances. The flu has since become a frequent massive killer in poultry farms in many parts of Southeast Asia. It has unusual staying power, persisting in different parts of the world since it emerged in 1997. Although the virus has not spread in humans, there is no way to tell what the virus will do as time passes; no one knows how long it took for the 1918 virus to develop the properties that led to a pandemic.

Meanwhile, evidence is pouring in that H5N1 seems to be breaking its way into more and more species. Once known to infect chickens, ducks, and occasionally humans who came in contact with these species, the virus is now found in a wide range of birds, and has infected cats, and even killed a tiger at the Bangkok zoo.

This summer, veterinarians had predicted that H5N1 might sprawl into Europe, after the virus -- previously limited to Southeast Asia -- turned up among migratory birds first in Western China, then in Mongolia, and finally, just over the Ural Mountains, a chain that divides Asia from Europe, in Russia and Ukraine. The bird flu is reported to have spread in Europe. Romania and Turkey reported first cases of avian influenza in early October, and both presumed to involve birds that migrate from Asia in autumn. Large bird flu outbreaks that occurred on chicken farms in the Netherlands in 2000, although unrelated to the Asian strain, killed 30 million birds, costing 100 million euros. The European Union now bans poultry imports from Asia as a result.

To limit the spread of bird flu, Romanian authorities killed hundreds of birds and then imposed quarantine on the villages and six counties in the area. In Turkey, after an outbreak of bird flu had occurred among turkeys on a farm in the western part of the country, the village was put under quarantine and all birds and street dogs were being killed as a precaution.

Many countries are preparing to protect its citizens in the event a pandemic flu lands on their soil. For example,

• Vietnam has a comprehensive plan that covers how government agencies responsible for everything from finance to tourism would respond to an epidemic.
• Japan has begun manufacturing its own Tami-flu, a costly antiviral medicine that until recently was made only in Europe.
• South Korea is one of several governments in the region that has run an elaborate simulation for how government agencies might respond to a wide outbreak of the disease.
• China's preparedness for avian flu is somewhat secretive. Authorities in Beijing have announced that they have a draft plan to deal with a pandemic, but have divulged few details.
• Hong Kong has more than 100 private and state-run clinics, and most of the territory's nursing homes and child care centers, now provide the government with weekly reports.
• Taiwan, was one of the earliest buyers of a Tami-flu stockpile two years ago, and plans to set up its own vaccine factory.

Avian flu in countries which are not prepared, for example, Cambodia and Laos, could become entrenched and out of control before the international health community even became aware of it, quickly spreading across borders and around the globe.

Fear of the bird flu sweeping across Asia has played a major role in the Bush administration's flurry of preparations for a worldwide epidemic. That concern prompted President Bush to meet with vaccine makers on October 7 to try to persuade them to increase production, and it led Health and Human Services Secretary Michael Leavitt to depart yesterday for a 10-day trip to at least four Asian nations to discuss planning for a flu pandemic.

Scientists in a high security-laboratory here in the US finally deciphered the genetic sequence of the devastating 1918 virus and have synthesised the lethal germ with promising implications. New York Times editorial calls this: "[A] scientific tour de force that should provide important insights on the best way to respond to the avian influenza strain now circulating in Asia." Two top US federal health officials said that the H5N1 virus has already acquired five of the 10 genetic sequence changes associated with human-to-human transmission of the 1918 virus. Nobody knows how likely it is that further mutations will occur, or how long the process may take.

The findings offer several promising prospects: the results offer specific leads to health officials who are preparing for a possible pandemic; medical experts are now able to prepare a checklist of the genetic changes and thus monitor the evolution of the avian flu virus and rush medical help to any area where on prompt notice; the results will help experts develop drugs and vaccines aimed at the most important genetic targets, thus allowing them to treat or even prevent influenza more effectively.

While many government in East Asia and the West now have some kind of a plan in motion for emergency response against a pandemic, the people of Bangladesh have a right to know what plan the government of Bangladesh has in store to save life and sufferings of the people. Whether the flu attack is on humans or birds, the only effective treatment is quarantine, and in case of birds, massive culls of any birds that are exposed.

When the H5N1 first emerged in 1997, in Hong Kong's tightly packed farms and markets, more than a million birds were killed in a day. Some people call it a blunt sledgehammer approach to defeat the virus, at a huge cost to farmers and governments.

In the event of a pandemic flu spreading in humans in Bangladesh, leaving the people to the mercy of God alone could kill millions before God's mercy brings in help from other nations.

Samantha M. Dewan is a medical student.