Bird Flu Pandemic: Not If, But When

Bird flu will break out of Asia and the world is pathetically unprepared to deal with it. And if the rapidly evolving disease mutates into a form that is easily transmissible among humans, millions will die in the ensuing pandemic in poor and rich countries alike, including an estimated half a million in the US. Vietnam recorded its 39th fatality on Thursday.

The US foreign policy establishment has pinpointed the newest Asian threat to the world - birds. More specifically, it is the probability - some say the inevitability - of a deadly avian influenza virus spreading across the world. As the old cliche goes, it is not a question of if, but when.

That avian flu is dangerous is no longer in doubt. Since the virus, known as H5N1 (a strain of avian influenza A virus), first emerged in Hong Kong in 1997, it has been responsible for the deaths of more than 60 people and millions of chickens, ducks and other poultry and fowl in Southeast Asia.

In fact, more than 100 million birds in the affected countries either died from the disease or were killed in order to try to control the outbreak.

The danger now is that the virus may mutate to become easily transmissible among humans and spread in a global pandemic in poor and rich countries alike.

According to a June 15 World Health Organization (WHO) report, Vietnam's Ministry of Health has confirmed a number of human cases of H5N1 virus infection.

And on Thursday, a 73-year-old Vietnamese man died from bird flu, taking the country's toll to 39, 19 of them since the virus returned in December, state-run media reported.

It is thought that a few cases of person-to-person spread of H5N1 viruses have occurred. For example, one instance of probable person-to-person transmission associated with close contact between an ill child and her mother is thought to have occurred in Thailand in September 2004.

More recently, possible person-to-person transmission of H5N1 viruses is being investigated in several clusters of human cases in Vietnam.

This week, the WHO repeated its warning that the H5N1 virus could mutate into a form which could pass easily between people and cause a global pandemic. "Because influenza viruses are inclined to change frequently, WHO advises Vietnam and the rest of the world to remain vigilant in its influenza control efforts," the WHO said in a statement.

"The risk of a pandemic remains, but with further research and international collaboration, the possibility of lessening its impact is a goal that may ultimately be realized," Hans Troedsson, WHO representative in Vietnam, said in the statement.

Just last week, China reported a new outbreak of deadly bird flu. The outbreak, the third revealed by China in the past two months, occurred at a farm in northwest China's Xinjiang region. At least 128 geese and ducks were infected and 63 of them were by the H5N1 strain of the virus, according to the United Nation's Food and Agriculture Organization

And last Friday, the WHO announced that a team of international experts was in Vietnam studying whether the H5N1 bird flu virus may be evolving into a form that might trigger a human pandemic.

The WHO says that an H5N1 pandemic could kill up to 7.4 million people globally, because people lack immunity to it. And half a million Americans could die and more than 2 million could end up in the hospital with serious complications if an even moderately severe strain of a pandemic flu hit, a report by the Trust for America's Health says.

In addition to Vietnam, outbreaks of H5N1 among poultry have been confirmed in Cambodia, China, Indonesia and Thailand during 2005, and in Malaysia and Laos during 2004.

This week, a Japanese farm is expected to cull most of its 25,000 chickens to prevent the spread of bird flu, identified as A H5N2, which has killed about 800 chickens. The H5N2 strain has not been known to cause any human illness cases, unlike H5N1.

The Japanese government ordered another 16 nearby farms in Ibaraki prefecture to suspend transportation of chickens and eggs. Japan had four outbreaks of avian flu in 2004, all involving the H5N1 virus.

The H5N2 strain of avian flu has been responsible for highly pathogenic outbreaks in Pennsylvania (1983-85), Mexico (1994-95), Italy (1997), Texas (2004), and South Africa (2004), according to the WHO report, "Assessing the Pandemic Threat".

The H5N1 strain is seen as such a danger that US-based Foreign Affairs journal, the preeminent status quo journal, has a special set of four articles on the subject in its newly published issue.

In the lead article author Laurie Garrett writes, "The havoc such a disease could wreak is commonly compared to the devastation of the 1918-19 Spanish flu, which killed 50 million people in 18 months. But avian flu is far more dangerous.

It kills 100% of the domesticated chickens it infects, and among humans the disease is also lethal: as of May 1, about 109 people were known to have contracted it, and it killed 54%."

Garrett also wrote that the H5N1 virus developed in ways unprecedented in influenza research. It is not only incredibly deadly, but also very difficult to contain.

The virus apparently now has the ability to survive in chicken feces and the meat of dead animals, despite the lack of blood flow and living cells; raw chicken meat fed to tigers in Thailand zoos resulted in the deaths of 147 out of a total of 418.

Indonesia this week announced that it was changing tactics in its fight against the H5N1 virus. Minister for Agriculture Anton Apriyantono is reported as saying that the country will shift from its controversial approach of killing only visibly ill birds and vaccinating others, to culling all poultry in outbreak zones.

Indonesia's policy change comes soon after the country found its first human case of H5N1, in a poultry worker who was not sick but carried antibodies of the virus.

Among other morbidly fascinating facts one of the Foreign Affairs articles notes that in early 2004 the virus became supervirulent and capable of killing a broad range of species, including rodents and humans.

That permutation of the virus was dubbed "Z+". In the first three weeks of January 2004, Z+ killed 11 million chickens in Vietnam and Thailand.

The economic impact of a pandemic would be staggering. In another Foreign Affairs article author Michael Osterholm notes that its arrival would trigger a reaction that would change the world overnight.

A vaccine would not be available for a number of months after the pandemic started, and there are very limited stockpiles of antiviral drugs. Plus, only a few privileged areas of the world have access to vaccine-production facilities.

Foreign trade and travel would be reduced or even ended in an attempt to stop the virus from entering new countries - even though such efforts would probably fail given the infectiousness of influenza and the volume of illegal crossings that occur at most borders.

It is likely that transportation would also be significantly curtailed domestically, as smaller communities sought to keep the disease out. The world relies on the speedy distribution of products such as food and replacement parts for equipment.

Global, regional and national economies would come to an abrupt halt - something that has never happened due to HIV, malaria or TB, despite their dramatic impact on the developing world.

Is the world prepared? Not really

First, the H5N1 flu strain and several of its cousins are ones to which humans have no immunity. This is because the H5N1 virus does not usually infect humans; thus there is little or no immune protection against them in the human population.

Second, as Nature journal pointed out in May, extinguishing avian flu in poultry and pigs, the population from which a pandemic strain would probably emerge, is the job of national agriculture and veterinary departments, the United Nations' Food and Agriculture Organization, and the World Organization for Animal Health.

The public-health aspects are the responsibility of health departments and the WHO. This international coalition is shaky and far from united or sure in its purpose.

Its efforts are grossly underfunded, and undermined at every turn by conflicts between global public health, sovereignty and the stakes of trade and economics.

Third, if the next pandemic were to arise in the near term, say the next two years, there would be no vaccine and few drugs to treat the virus.

Currently, a vaccine against a pandemic flu would not be ready until at least six months after a pandemic starts. Too late: by then the worst of the pandemic would already have happened.

Fourth, although a pandemic would be global, defense plans are so far strictly national. So far, due to prodding by the WHO, about 50 countries have drawn up preparedness plans. Most are still very sketchy, but include strategies for stockpiling antiviral drugs.

Only a handful of nations, including Britain and Canada - but notably not the United States - have given their plans legal status.

Distressingly, the list of relatively well-prepared nations includes few of those countries in Asia where a pandemic strain is most likely to emerge.

Finally, it is also notable that the H5N1 virus has continued to evolve. In late 2002 it acquired the ability to kill its natural host, wild waterfowl, and spread across 10 countries in Southeast Asia. The virus has also found ways to vastly increase the range of species it can infect and kill.

Its host range now includes tigers and domestic cats. The concern is now whether it will acquire consistent human-to-human transmission.

Most strains of influenza are not lethal in lab mice, but Z+ is lethal in 100% of them. It even kills the very types of wild migratory birds that normally host influenza strains harmlessly.

Yet domestic ducks, for unknown reasons, carry the virus without a problem, which may explain where Z+ hides between outbreaks among chickens.

Influenza reproduces messily: its genes easily fall apart, and it can absorb different genetic material and get mixed up in a process called reassortment.

When influenza successfully infects a new species - say, pigs, as happened with the emergence of the Nipah virus in Malaysia in 1999 - it can reassort, and may switch from being an avian virus to a mammalian one. When that occurs, a human epidemic can result.

The WHO highlights the need for the world to take action well before "there is unmistakable evidence that the virus has become sufficiently transmissible among people to allow a pandemic to develop".

David Isenberg @ Asia Times

tags: birdflu  pandemic  asia  

links: digg this    del.icio.us    technorati    reddit