12 August 2005

Death on a Wing

A flu pandemic that could strike without warning and kill millions is on its way.

With the world economy locked into open trade and globalisation, and security wracked by terrorism and fundamentalism, you could forgive the planet’s leaders for being distracted. It’s hard to conceive of anything so tumultuous that it could deliver us beyond the post-September 11 era of suicide bombers and chronic poverty, religious fanaticism and rampant militarism, of record profits and jaded celebrities, cosmetic surgery and low interest rates.
Nothing, except a global influenza pandemic. With the conditions ripe and the world overdue for another global outbreak, government and corporate decision-makers have been jolted in recent months to consider the consequences.

Human flu pandemics spread quickly to all parts of the globe and typically infect more than a quarter of the total population. They deliver high levels of morbidity and mortality and cause major social disruption. There were three pandemics in the 20th century: in 1918, 1957 and 1968. In 1976, governments planned for an outbreak that never came. And there have been false alarms, where novel strains of the virus have been identified but have ended in few cases and limited human-to-human transmission. But in January 2004, health officials became alarmed at the outbreak in humans of a new and dangerous strain of the virulent H5N1 virus, better known as avian or bird flu in Asia. Officials believe all the prerequisites for the start of an influenza pandemic have been met save one: the establishment of efficient and sustained human-to-human transmission of the virus.

After H5N1’s first appearance in humans, in Hong Kong in 1997 when six out of 18 confirmed cases died, the spread ceased after authorities culled Hong Kong’s entire chicken population of 1.5 million. But the virus itself did not disappear. It simply retreated to China’s southern Guangdong province, where it had first been identified in ducks. Between 1998 and 2003, H5N1 evolved through 17 strains at high speed, becoming more pathogenic and resilient, hopping hosts from wild to domestic birds, and to mammals such as pigs and, since 2004, to humans again. The United Nations’ Food and Agriculture Organisation says 140 million birds have died or been destroyed and the combined losses to gross domestic product are estimated at $US10bn to $US15bn ($12.97bn to $19.45bn). Since the first case in Vietnam in December 2003, there have been 111 laboratory-confirmed human cases of avian flu, with 57 deaths in Vietnam, Thailand, Cambodia and now Indonesia. What has virologists worried is the potential of H5N1 to recombine into a virulent new human-to-human strain, capable of unleashing an unprecedented contagion around the world that would kill millions.

With the first official instance of human-to-human transmission reported in September 2004 in Thailand, the World Health Organisation declared the world had now “moved closer to a new pandemic than it has been at any time since 1968”. In February this year, WHO announced it had entered the pandemic alert period – phase three in its six-phase alert scale, where there are incidents of human infection with a new strain but as yet no human-to-human spread. Some experts believe we have already moved to phase four, with confirmed clusters of cases of human-to-human transmission in Vietnam and China and, last month, in Indonesia. More recently, the fact that migratory birds had spread the virus from western China to Russia’s European frontier in just three weeks – spurring five suspected human cases in northern Kazakhstan – have pushed consensus on the near-term probability of a pandemic from “if” to “when”.

How the pandemic would devastate Australia. If a pandemic with an attack rate of 25% (one-quarter of the population affected) were to occur again in Australia and there was no vaccine or treatment available, over a six-eight week period it could lead to:
* 13,000 to 44,000 deaths
* 57,900 to 148,000 hospitalisations
* 2.6 to 7.5 million outpatient visits.
The figures are estimates only and the likely outcomes associated with a pandemic will depend on many factors such as the transmissibility and virulence of the virus, and the availability and success of health and social interventions.
(Source: Australian Government Management Plan for Pandemic Influenza)


With the virus permanently established in birds in large parts of Asia, “the threat to human health will persist as long as the problem persists in animals”, says Dr Peter Horby, public health expert with WHO in Hanoi. Alarmed by the inadequacy of national and international plans to cope with such a global health emergency, two respected American journals, Foreign Affairs and Nature, in a co-ordinated effort devoted their July issues to “The Next Pandemic”.

In the so-called Spanish Flu of 1918, 400 million people were clinically infected and more than 40 million people perished, out of a global population of 2 billion. A pandemic of that order today would kill between 180 million and 360 million people within 18 months. World trade and international travel would be brought to a standstill, plummeting productivity would usher in economic depression, and the short supply and unequal distribution of effective drugs, coupled with overwhelmed public health facilities, quarantines and restrictions on the movement and association of citizens, would lead to social unrest that would destabilise governments everywhere, notwithstanding the exponential increase in security threats from insurgents and terrorists. Michael T. Osterholm, an infectious disease expert for the American Department of Homeland Security, writes in Foreign Affairs: “The reality of the coming pandemic ... cannot be avoided. Only its impact can be lessened.”

That’s the worst case scenario we should prepare for if we are to heed the warnings of respected health experts. The messages are getting through. In recent weeks, governments, international agencies and corporations have taken steps to brace for the coming calamity. Scientists, while alarmed, still cannot tell us when the pandemic will occur — it could be tomorrow, in six months or six years. But they have told political leaders it’s time to scramble, to begin planning for the worst and hoping for the best.

Still, no politician wants to risk being called Chicken Little. Federal Health Minister Tony Abbott told reporters last week: “There’s a fine line to be trod here between scaring people over something that might never happen and alerting people to something that may very well happen.” The federal government has walked that fine line in recent months, implanting the notion of pandemic preparedness into the public’s brain stem, while emphasising that we’re still in a “no worries, she’ll be right” phase.

Following WHO’s lead, Australia in March went to “Overseas Three” in its own six-step pandemic scale. In June, the government’s “Management Plan for Pandemic Influenza” was launched, along with a new slogan: Prepared and Protected. Abbott laid out Australia’s game plan: “The initial objective would be to attempt to prevent its appearance in Australia for as long as possible. Once there was a case in Australia, we would be determined to limit its spread within this country for as long as possible. And once there was a widespread outbreak, treatment and prevention, prophylaxis, would be our principal objective.”

Estimated deaths
* 1918 pandemic 40 million
* World War I 8.3 million

With WHO estimating at least a six-month lag from outbreak to the development of an effective vaccine, much has been made of the efficacy of the key anti-viral agent oseltamivir, with the tradename Tamiflu. Recent reports that the government has “cornered the world market” in Tamiflu ignore conflicting evidence that many of those infected with H5N1 who took Tamiflu still died, often from the secondary pneumonias that take the heaviest toll in such pandemics. “In responding to a pandemic,” Osterholm notes in Foreign Affairs, “Tamiflu could have a measurable impact in countries with sizeable stockpiles.” Like Australia. But there is “no evidence” that Tamiflu helps if the patient develops the “cytokine storm that characterises the recent H5N1 infections”. Here the immune system fights the virus with such ferocity that the lungs in a sense melt and the patient suffocates.

Public statements from all sides of politics in recent days reflect a lack of engagement with the nature of the threat identified by experts. Greens senator Bob Brown has called for Tamiflu to be sold over the counter, instead of only by prescription. The distinction is moot if there isn’t enough to go round. If the pandemic obliges by striking when we are ready, there will still only be one dose available for every five Australians. Latest clinical trials indicate the effective dose of Tamiflu is much higher than previously expected, meaning even less of the drug to go round. As for vaccine, Osterholm predicts it “would have no impact on the course of the virus in the first months and would likely play an extremely limited role worldwide”. And the government’s agreements with two overseas vaccine manufacturers may come to nothing should their host countries nationalise vaccine production in the event of a pandemic, as the US did in 1976 when it refused to share vaccine for the swine flu pandemic it was expecting but never came.
In a speech to the Australia Indonesia Business Council on August 1, Labor foreign affairs spokesman Kevin Rudd identified “one of the key challenges in the early detection of bird flu was the reluctance of poultry farmers to report the disease for fear their entire flocks, and livelihoods, would be destroyed”. It may be a challenge in China, but for Australia the more pressing concern is when the human-to-human transmission takes hold and the disease sweeps in like any of the “normal” seasonal flus. In this situation, border protection becomes immaterial. According to Foreign AffairsLaurie Garrett, “No nation can erect a fortress against influenza ... national policy-makers would be wise to plan now for worst case scenarios involving quarantines, weakened armed services and dwindling hospital space and vaccines.

“The greatest weakness that each nation must individually address is the inability of their hospitals to cope with a sudden surge of new patients ... the potential for pandemic comes at a time when the world’s public health systems are severely taxed and have long been in decline.”
In this context, last week’s announcement by Abbott and state health ministers that they would stage a “mock outbreak” in December to test hospital capacity will be scrutinised – that’s if we get the luxury of having a trial run. The government’s worst case estimate is that in the event of a pandemic, 2.6 million people would need medical attention, with up to 148,000 hospitalised. We should expect that these numbers will be put to the test.

In the event of a pandemic, the flow of free and accurate information will be more than an ethic; it will be a matter of public health and safety. The last time the spectre of 1918 was invoked was in 1976 when US President Gerald Ford put the nation on alert. Swine flu never materialised, and Ford and confidence in the US public health system were damaged.

Chinese authorities were heavily criticised for suppressing news of the SARS outbreak, and then minimising its seriousness. Now there are worrying signs again from China. In July, a Hong Kong laboratory had its research on the H5N1 strain suspended by China’s Ministry of Agriculture. The ministry also dismissed research by the lab on the recent H5N1 outbreak among migratory birds in western China. The WHO has complained that China is not sharing samples of the outbreak strain.

All this highlights the need for international organisations like the WHO to be free to monitor any pandemic impartially. However, such organisations are critically under-resourced. The WHO has an annual budget of just $400m, and can intervene only when invited by a country.

* H5N1 has found a new ecological niche in poultry in parts of Asia.
* The virus is now more deadly in poultry and in the mammalian mouse model.
* New animals – cats and tigers – are becoming infected for the first time, suggesting the virus is expanding its host range.
* Domestic ducks are excreting large quantities of virus without showing symptoms.
* Viruses from 2004 survive longer in the environment than viruses from 1997.
* The virus is killing at least some wild migratory birds.
* These changes have created multiple opportunities for a pandemic virus to emerge.

    First published in The Bulletin

    No comments:

    Post a Comment