Antiviral Drug Donation Eases Fear of Bird Flu Pandemic

GENEVA, Switzerland, August 24, 2005 (ENS) - A dangerous form of avian influenza identified in Russia and Kazakhstan increases the probability that humans could be exposed to the deadly flu strain, the World Health Organization (WHO) is warning. But a note of hope was introduced today, as WHO officials welcomed a donation of three million treatment courses of an antiviral drug from the multi-national pharmaceutical company Roche.

WHO will add the drug, oseltamivir or Tamiflu, to its international antiviral stockpile and would use this stockpile to respond quickly to an emerging influenza pandemic. WHO considers the present risk of a pandemic to be "great," but unpredictable in terms of its timing and severity.

"Right now, many wealthy countries are creating their own stockpiles of antivirals. However poor countries simply cannot afford to do this. If a flu pandemic were to emerge in a poor country for example, these drugs could be flown quickly to the center of a potential pandemic," said Dr. Lee Jong-wook, director-general of WHO, during an influenza news conference today in Geneva.

World Health Organization Director-General Dr. Lee Jong-wook has plans to combat a global flu pandemic, but warns that early detection is crucial and surveillance needs improvement. (Photo courtesy WHO)

The prospect of halting a pandemic at its source or delaying its international spread is attractive, but untested, as no attempt has ever been made to alter the natural course of a pandemic.

Roche has agreed to reserve three million treatment courses (30 million capsules) for up to five years. The first one million treatment courses (10 million capsules) will be ready early next year, with the remaining two million (20 million capsules) ready before mid-2006.

Russia and Kazakhstan began detecting the disease in birds in late July, and confirmed the presence of the H5N1 strain in August. The infection has led to the deaths or destruction of almost 130,000 birds in the two countries. WHO officials warned in a situtation assessment Thursday that the possible spread of H5N1 avian influenza to poultry in additional countries cannot be ruled out.

The highly pathogenic H5N1 viral strain, circulating in Southeast Asia since it was discovered in Hong Kong in 2003, has caused the deaths of more than 150 million birds in the region.

The virus also has infected humans, with 112 confirmed cases resulting in 57 deaths in four nations - Vietnam, Thailand, Cambodia and Indonesia.

No human cases of bird flu have been detected in Russia and Kazakhstan.

Health experts worry that H5N1 could develop into a virus that is easily transmitted between humans. If that happens, global spread of the disease could occur and potentially kill tens of millions of people. But to date, WHO officials say, only a few instances of limited human-to-human transmission have been recorded.

Dr. Lee admitted today that the world's surveillance system is not strong enough to detect every human case. "We urgently need to improve the early warning system to detect outbreaks in animals and humans," he said. "This is an essential prerequisite for using the antiviral most effectively."

"We need to coordinate research and accelerate the development of pandemic vaccine," the WHO chief said. "We need to provide incentives to poorer countries to become more involved in an international effort."

Pigs, ducks and chickens mingle in this Laotian farmyard. This is considered a dangerous situation as avian flu can infect pigs that can also pick up human viruses. The two viral strains could breed in pigs, creating a strain that could be transmitted easily from human to human. (Photo by Ray Webb courtesy FAO)

Deaths in migratory birds infected with the virus have also been reported. Outbreaks in both countries have been attributed to contact between domestic birds and wild waterfowl through shared water sources.

These are the first outbreaks of highly pathogenic H5N1 avian influenza recorded in the two countries, previously considered free of the virus.

Since the initial reports, the Russian H5N1 outbreak in poultry, which has remained confined to Siberia, has spread progressively westward to affect six administrative regions.

In Kazakhstan, poultry in several villages bordering the initial outbreak site in Siberia are now known to have experienced the disease.

Outbreaks in the two countries have involved large farms as well as small backyard flocks, with close to 120,000 birds dead or destroyed in Russia and more than 9,000 affected in Kazakhstan.

In early August, Mongolia issued an emergency report following the death of 89 migratory birds at two lakes in the northern part of the country. Avian influenza virus type A has been identified as the cause, but the virus strain has not yet been determined. Samples have been shared with WHO reference laboratories and are currently being investigated. Also in early August, an outbreak of H5N1 in poultry was detected in Tibet.

In all of these recent outbreaks, authorities have announced control measures in line with recommendations for highly pathogenic avian influenza issued by the UN Food and Agriculture Organization (FAO) and the OIE.

"To date, no human cases have been detected, vigilance is high, and rumours are being investigated by local authorities," WHO officials said in a situation assessment on Thursday.

Experience in southeast Asia indicates that human cases of infection are rare, and that the virus does not transmit easily from poultry to humans, WHO said in its assessment. The majority of human cases have occurred in rural areas, and most, but not all, human cases have been linked to direct exposure to dead or diseased poultry during slaughtering, defeathering, and food preparation. No cases have been confirmed in poultry workers or cullers.

No cases have been linked to the consumption of properly cooked poultry meat or eggs.

Vietnamese man with avian influenza is treated in hospital (Photo credit unknown)

Poultry outbreaks of H5N1 avian influenza in Japan, Malaysia, and the Republic of Korea were successfully controlled.

All three agencies agree that control of avian influenza infection in wild bird populations is not feasible and should not be attempted. Wild waterfowl, such as ducks and geese, have been known for some time to be the natural reservoir of all influenza A viruses, including the H5N1 strain.

Migratory birds can carry these viruses, in their low pathogenic form, over long distances, but do not usually develop signs of illness and rarely die of the disease. The instances in which highly pathogenic avian influenza viruses have been detected in migratory birds are rare, and the role of these birds in the spread of highly pathogenic avian influenza remains poorly understood, WHO officials said.

Very large die-offs of migratory birds from avian influenza, such as the one detected at the end of April at Qinghai Lake in central China, in which more than 6,000 birds died, are considered unusual. Research published in July indicates that H5N1 viruses in that outbreak are similar to viruses that have been circulating in southeast Asia for the last two years.

Analyses of viruses from the Russian outbreak, recently published on the OIE website, show apparent similarity to viruses isolated from migratory birds during the Qinghai Lake outbreak.

Monitoring the spread and evolution of avian H5N1 viruses in birds and rapidly comparing these results with previously characterized H5N1 viruses is an essential activity for assessing the risk of pandemic influenza.

Officials recommend heightened surveillance for outbreaks in poultry and die-offs in migratory birds, and rapid introduction of containment measures.

Health workers are advised to exercise greater vigilance for cases of respiratory disease in persons with a history of exposure to infected poultry in countries with known poultry outbreaks.

"Each additional human case increases opportunities for the virus to improve its transmissibility, through either adaptive mutation or reassortment," WHO said. "The emergence of an H5N1 strain that is readily transmitted among humans would mark the start of a pandemic."

WHO says that successful intervention to stop a pandemic requires that at least five conditions be met:

• The first viruses that show an ability to sustain transmission among humans will not yet be highly contagious.
  
• The emergence of such viruses will be limited to a small geographical area.
  
• The first clusters of human cases caused by the virus will be rapidly detected and reported.
  
• Antiviral drugs will be rapidly mobilized from the stockpile, made available to the affected population, and administered to sufficiently large numbers of people.
  
• Movement of people in and out of the area will be effectively restricted.