Preparing to battle a crisis in the future

Health officials focus on ways to slow global spread of viruses such as avian flu

October 20, 2006|By Frank D. Roylance | Frank D. Roylance,sun reporter

Haunted by the knowledge that influenza killed 50 million people in 1918, scientists and public health officials continue to seek ways to head off the next great pandemic.

They are focused mostly on the lethal avian influenza that's spreading among birds and some of their human caretakers from Asia to Europe and Africa.

The virus is killing humans at a rate of one every four days - 73 this year - or twice last year's pace. And its spread increases the chance it will swap genes with a human flu virus, producing a hybrid that will be easily spread and deadly among people.

So far, the human toll has been relatively small in a global context. The bird flu virus seems to have a difficult time jumping from birds to people.

But scientists are on alert for signs of a genetic shift that could transform the bird disease into something capable of killing millions, disrupting daily life and commerce across the globe.

Others are looking for the best way to construct a vaccine, or antiviral drugs, to prime our immune systems to grapple with the more dangerous virus that may evolve from the avian flu.

And public health officials are working to devise the most effective ways to slow the spread of a pandemic, to hold mass vaccinations and keep essential services running despite absenteeism.

It's an unprecedented mobilization against a virus that doesn't yet exist, officials note. And it's never been done for any influenza virus, despite the substantial death tolls from the annual flu - a complacency that has begun to dissolve.

"The lack of adequate preparation on a yearly basis for a highly predictable seasonal flu is one of the reasons we are now in crisis mode with pandemic flu," said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases.

Known officially as avian influenza A (H5N1), the bird flu virus is not the same virus that carried illness and death around the planet in 1918 and 1919.

But scientists have found similarities to the 1918 bug, which they have reconstructed from DNA extracted from human tissues saved since the First World War, and chipped from the dead in an arctic grave.

They believe the 1918 virus evolved from an A-type bird flu virus that jumped to humans. Without any past exposure to anything like it, human populations had little or no ready immunity. Nearly everyone was exposed to what was known as "Spanish flu" and death rates reached 8 percent in some places.

The H5N1 avian flu virus is also a Type A avian influenza. Its least-destructive (low pathogenic, or "low-path") form is common in the guts and saliva of wild birds, and easily spread, though rarely fatal to them.

What has scientists worried is that a highly pathogenic ("high-path") strain of H5N1 has emerged. It can kill wild birds and burns through domestic flocks, killing 90 percent to 100 percent of the flocks in a day or two.

That puts the virus in close proximity to people, who are falling ill and dying in increasing numbers. The World Health Organization said this week that 256 people in 10 countries are known to have been sickened by the H5N1 virus since 2003. Of those, 151 have died. That's a 59 percent mortality rate.

Until now, most deaths occurred among people in close contact with sick birds. Among the cases announced this week was a 67-year-old woman who died in West Java, part of Indonesia. She fell ill after her household chickens began to die.

Another was an 11-year-old boy from South Jakarta. He, too, had been fatally exposed to dead chickens in his neighborhood, the WHO said. Indonesia is the current hotspot, with more cases this year than any other nation.

The H5N1 virus is still having a hard time spreading directly between people. But it can, and does.

In June, WHO described a case in Indonesia where one person was infected during contact with infected poultry. He then spread the illness to six family members, and one of those six - a child - infected his own father.

Researchers studying the virus' species-jumping capacity have already reported infections in domestic pigs - frequently a source of illness for humans - wild and domestic cats, dogs and a weasel-like animal in Germany.

So far, the highly pathogenic H5H1 strain has not been found in the Americas. But surveillance continues of migratory bird populations that might bring it here.

The U.S. Centers for Disease Control and Prevention and the federal departments of interior and agriculture said recently that they had found evidence of the H5 and N1 proteins in pintail ducks in Ohio, mallards in Pennsylvania and teals in Illinois. But they said these were likely from separate viruses, or the low-path strain of the H5N1 virus.

"We have done close to 20,000 samples for wild birds in North America ... and none of those samples has been positive for the high-path Asian H5N1 form," said Hon Ip, director of the National Wildlife Health Center's diagnostic virology lab in Madison, Wisc.

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