January 14, 2004
WHO Caution: Bird Flu Could Be Precursor To Influenza Pandemic
Experts have warned that the bird flu outbreak that claimed 12 lives in Vietnam could be the precursor to an influenza pandemic.
Flu pandemics occur when a new influenza virus arises and acquires the ability to spread within the human population. The entire global population could be susceptible. Huge numbers of people fall ill and millions die.
"The ingredients are there that the pandemic can occur," Klaus Stohr, project leader of the World Health Organization's global influenza program, said in an interview from Geneva.
"We can hope for the best but we are preparing for the worst."
Public health authorities have been predicting for some time that the world is overdue for a new pandemic, which would sweep the globe, killing millions and causing far-reaching social and economic disruption.
The most deadly example of an influenza pandemic was the Spanish Flu of 1918-19, which killed between 20 million and 40 million people worldwide.
Recent outbreaks of avian influenza of the H5N1 subtype in South Korea, Japan and now Vietnam - and repeated transmission of the virus to humans - may be laying the groundwork for that dreaded event, influenza experts warned.
"The more times that there are outbreaks amongst poultry and the more times that there are human exposures and human cases of H5N1, the more opportunities there are for this influenza virus to mutate to the point where it is well adapted for human-to-human transmission," noted Dr. Danuta Skowronski, an influenza specialist at the British Columbia Centre for Disease Control.
Health Canada is maintaining a high level of vigilance, monitoring the situation on a constant basis, said Dr. Arlene King, director of the immunization and respiratory infections division.
"Certainly it represents a concern and a health threat. And that's why we take these things very seriously."
Parts of southern Vietnam are in the grips of an H5N1 influenza outbreak among poultry stock. The virus, which is fatal in virtually all chickens it infects, has killed upwards of one million chickens so far. The Vietnamese government is culling tens of thousands more birds in a bid to contain the outbreak.
But in other parts of Vietnam, the virus has attacked humans. Laboratory testing has confirmed H5N1 infection in two children and an adult in the capital, Hanoi.
WHO spokesman Dick Thompson said the organization is investigating a total of 14 suspected cases of bird flu in humans in Hanoi and surrounding provinces. All but one of the cases were children. Twelve of the 14 cases - including 11 children - have died.
Officially, the WHO says there is no evidence of human-to-human transmission of this strain of influenza, though Stohr admitted there may have been "some very inefficient transmission from human-to-humans."
But some of the infections date back to late October, a worrisome sign. The longer bird flu is in contact with humans, the greater the chance it will acquire the ability to spread among them.
And WHO is aware that these 14 cases may not be the entire iceberg.
"There is a concern that there could be more cases out there, both in humans and in chickens," Thompson admitted, saying the WHO has asked other countries in the region to be on the lookout for "any unusual patterns of death in chickens or humans, influenza-related."
For a pandemic to occur, a strain of influenza which has never before circulated among humans has to break out of nature and develop the ability to spread not just from animals to humans, but from human to human as well. Virtually no one would have any real immunity to such a virus, meaning it would spread like wildfire around the globe, rendering huge numbers of people sick.
Most people recuperate from influenza. But some go on to develop pneumonia and die, as Canadians have been reminded this severe flu season. Health Canada estimates between 9,000 and 51,000 Canadians could die in the next pandemic, if a vaccine is not available.
Such widespread illness and death would cause massive disruption to the health-care system and would tax the ability of governments around the globe to maintain essential services, experts predict.
"A pandemic of influenza will make SARS look like a cakewalk in comparison," Skowronski said.
There are two ways an animal influenza virus can acquire the ability to spread within the human population - through a chance mutation that would give it that skill, or by what's called reassortment. If a person who was sick with a human influenza virus also became infected with the H5N1 virus, the two could swap some genetic material, and a new and deadly human virus could be formed.
Given that it is currently influenza season, that second option is particularly worrisome.
"It's a bad time for this to be happening," said Richard Webby, a leading influenza virologist based at St. Judes Children's Hospital in Memphis, Tenn.
"It's very, very concerning."
Stohr said the WHO has alerted its influenza network to the situation and will begin work on vaccine development within days. That process automatically kicks in when two or more human cases of avian influenza are discovered.