TWN Info Service on Health Issues No. 2

Imminent flu pandemic may kill millions, warn WHO experts

By Martin Khor
Geneva, 18 May 2005

International health experts warned Wednesday at the World Health Assembly that an influenza pandemic is imminent, and it could threaten the lives of several millions of people and cause severe economic and social dislocation.  They urged countries to have national strategies to counter the threat.

The warning was given at a WHO technical briefing to WHA participants. In a brief introduction, WHO Director-General Dr Lee Jong-wook said this session was perhaps the most important of the meetings being organized during the WHA. At the WHA opening on Monday, he had described the avian influenza as "the most serious health threat the world is facing today."

At Wednesday's briefing, WHO's influenza programme coordinator, Dr Klaus Stohr, called for global and national pandemic preparedness as "we are on borrowed time", with an increasing risk of pandemic in Asia. The cases of the influenza strain H5N1, which had so far infected 74 and killed 49 people (as of mid-March), were described by him as "the tip of the iceberg."

Stohr said that an influenza pandemic could make 500 to 1,253 million people ill, require 6.4 to 28 million people to be hospitalized (if there were enough hospitals running at that time), and result in 2 to 7 million deaths.

In reply to a question, Stohr said the data was from a model based on the pattern of mortality and morbidity from previous influenza pandemics in 1957 and 1968. The projections were based on present demography data and extrapolations on what would happen if there was no improvement in medical services and no change in the rapidity by which the virus will spread.

Stohr predicted that a pandemic would come in several waves, would affect community services and cause social and political disruption, with large economic losses. The present Asian avian flu epidemic was already predicted to cause $10-30 billion in losses. The impact of a pandemic in the US alone has been estimated to cause $170 billion in losses.

He urged countries to establish a national pandemic preparedness plan to respond to the imminent health emergency. Elements of the plan should incorporate health services, pharmaceuticals (including stockpiling vaccines and anti-viral drugs), civil emergency response, communication and leadership and coordination.

An international pandemic response system would support the national plans, he said, adding that so far 50 countries had such a pandemic preparedness plan but the WHO was unable to assess their quality.

Stohr said only a small number of countries would have access to vaccines or anti-virals due to the price factor and the limited capacity to produce these. Therefore, most countries would have to rely on non-pharmaceutical measures to reduce virus spread and improve medical care.

Richard Nesbit, from the WHO Western Pacific regional office, said the H5N1 influenza virus was undergoing constant genetic change and causing high fatality in humans. So far, 160 million poultry in Asian countries had died or were destroyed by the disease, which had now affected chickens, ducks, geese, ostrich, peacock, pigeons as well as domestic cats, tigers, and leopards.

There were now 76 cases in Vietnam, 17 in Thailand and some cases in Cambodia. A WHO meeting on 6-7 May in Manila had concluded that more infections were expected in humans, the H5N1 viruses are becoming more antigenically diverse, and there was a concern that the virus could be adapting to humans and increasing the pandemic potential.

The session also revealed that human-to-human transmission of the virus was now beginning to take place. The spread of the disease to humans has so far been limited because almost all the victims are thought to have contracted it from animals.

The great concern is that if the virus mutates so that it can be transmitted via human beings, then the risk of a pandemic would increase dramatically.

Dr. K. Ungchusek of the Ministry of Health, Thailand, reported a case in his country where a girl had died of pneumonia after being infected by the influenza virus, and her mother (who had taken care of her) had also died a few days later of the same type of ailment, while her aunt also fell sick (but did not die) from the disease.

He said that medical colleagues in neighbouring countries had also reported to him of family-based clusters of people contracting the disease, for example, three brothers at Thai Binh-Hanoi and five family members in Haiphong (both in Vietnam) and a brother and sister in Kampot province of Cambodia.

He added that Thailand (with 17 confirmed cases and 12 deaths) had adopted a strategic plan costing $100 million to stop the pandemic at source. The plan includes surveillance and cluster investigation; isolation and treatment of cases; target anti-viral prophylaxis for contacts; quarantining of contacts; social distancing; and vaccines for new viral strain.

Lenie Kootstra of the Dutch Health Ministry said that recent threats of infectious diseases are a cause of concern, including SARS, bio-terrorism, avian flu and Marburg virus. Holland had an avian flu outbreak in 2003, and 30% of the poultry had to be killed. There were also 13 human cases of flu-like illness with one death (a vet who had fought the epidemic).

Holland was now preparing a priority-delivery contract with a Dutch manufacturer to produce vaccines, but would like the optimal use of scarce production capacity at the EU level and beyond. She advocated global partnerships to face the risk.

From the floor, some participants raised the question of equity in treatment, as only a few countries would have access to scarce and expensive drugs.

A WHO official replied that the organization was aware of the equity issue, and would try to obtain cheaper drugs. The WHO has a stock of anti-virals for the influenza, which could be provided to countries facing an outbreak, but it did not have a stockpile of vaccines.

A WHO paper on "Strengthening pandemic influenza preparedness and response" (A58/13), prepared for the WHA, states that since January 2004, events have brought the world closer to an influenza pandemic than at any time since 1968. These events have given the world an unprecedented warning that a pandemic may be imminent.

There is recent evidence that the virus is evolving in ways that increasingly favour the start of a pandemic, says the paper. The H5N1 virus is now endemic in parts of Asia, with a permanent ecological niche in poultry. It has become progressively more pathogenic for poultry, and is now hardier than in the past, surviving longer in the environment.

The virus is also expanding its mammalian host range, having recently caused disease and death in species (including captive tigers and experimentally infected domestic cats) not previously considered susceptible to disease caused by any influenza A virus.

The paper says the most recent cases in Vietnam "suggest some new patterns of infection, including more clusters of cases possibly involving human-to-human transmissions, cases in older patients with mild or asymptomatic infection, the first case in a health-care worker, and the first case in an agricultural worker."

Taken together, these changes in the ecology of the disease and behaviour of the virus have created multiple opportunities for a pandemic virus to emerge, either due to exchange of genetic material between human and avian viruses (during co-infection of a human being or pig), or a more gradual process of adaptive mutation.

The paper adds that in the previous century there were three pandemics. Those beginning in 1957 and 1968 together caused more than 3 million deaths. The 1918 pandemic caused more than 40 million deaths.

"The present situation may resemble that leading to the 1918 pandemic. Similarities between the H5N1 and 1918 viruses have been suggested in the gradual adaptation of an avian to a human-like virus, the severity of the disease, its concentration in young and healthy people, and the occurrence of primary viral pneumonia in addition to secondary bacterial pneumonia."

The paper adds that the vulnerability to a H5N1-like pandemic is universal, since no virus of the H5 subtype has probably ever circulated before among human beings and certainly not in the present lifetime of today's world population. Rapid international spread is certain once a virus of this type appears, especially through air travel.

In relation to vaccines, the WHO paper says the greatest problem is inadequacy of supplies to meet global needs. Manufacturing capacity is limited and cannot be expanded quickly. Should a pandemic begin now, no company could meet its production targets.

Antiviral agents, which can be stockpiled in advance, have important roles but these are constrained by high costs and limited supplies.

A range of non-medical interventions can slow the spread of a pandemic. They include improved personal hygiene, quarantine, contact tracing and travel restrictions. A new document, "WHO checklist for influenza pandemic preparedness planning", is available to help countries in their strategies.