Global pandemic likely, health authorities say
updated 1:30 p.m. PT, Sun., Dec. 14, 2003
NEW YORK - As bad as this year’s flu season is, it hasn’t brought the worldwide outbreak known as a pandemic. But experts warn that a pandemic is coming, it’s just a question of when.
“It’s going to happen,” said Dr. Greg Poland of the Mayo Clinic. “For the American public in particular, I think it will be horrific.”
Many Americans haven’t experienced the overwhelming crush of patients at hospitals and doctors’ offices and the widespread fear a flu pandemic could bring. And by historical pattern, Poland said it’s about time for the next one.
There have been three in the past 100 years, igniting in 1918, 1957 and 1968. There’s no way to predict when the next one will appear, but the pattern does give experts pause.
It’s all up to a virus that is variable and fickle, constantly changing its genetic makeup, and the time when it hits upon a combination that lets it take off worldwide is a “roll of the genetic dice,” said Dr. William Schaffner of Vanderbilt University.
'It makes us nervous'
So the lack of a pandemic in the past 35 years basically means “the genetic dice haven’t been rolled that way,” Schaffner said. “While we’re grateful for that, it makes us nervous.”
There’s plenty to be nervous about. It’s estimated that in the industrialized nations alone, the next pandemic is likely to send 1 million to 2.3 million people to the hospital and kill 280,000 to 650,000, according to the World Health Organization. Its impact will probably be greatest in developing countries.
As a practical matter, flu shots probably could not be counted on to prevent a pandemic. For one thing, pandemic virus strains emerge unexpectedly, and there would probably not be enough time to recognize the threat and then provide vaccines that target them, Schaffner said. What’s more, many countries outside the United States wouldn’t have the means to give enough flu shots to stop the spread, Poland said.
Dr. Robert Couch of the Baylor College of Medicine noted that health authorities are making major efforts to prepare for controlling a pandemic, including putting an emphasis on developing and manufacturing vaccines faster and in greater quantities.
The pandemic of 1918-19, known as the Spanish flu, sickened an estimated 20 percent to 40 percent of the worldwide population, with a death toll believed to exceed 20 million. In the United States alone, some 500,000 people died. An ordinary flu epidemic kills an average of 36,000 Americans.
The next pandemic, the Asian flu of 1957-58, killed about 70,000 in the United States, while the 1968-69 Hong Kong flu led to about 34,000 deaths in the United States. Scientists suggest several reasons why this rate was lower than in previous pandemics, including that the illness did not gain momentum until near the school holidays in December, when children were home rather than infecting each other at school.
Flu viruses start in rural Asia
New strains of the flu virus, and so potential pandemics, get their start in rural Asia, where the various strains that infect chickens and other birds, pigs and humans can mingle. That gives them a chance to swap genetic information as well as mutate on their own.
The potential spark for a pandemic occurs when that environment produces a new virus that infects people and bears surface proteins that people’s bodies have never seen before. That means people have no natural defense against it.
In contrast, ordinary outbreaks like this year’s come from a virus that has changed only slightly from previous ones, so that the population it enters still has some natural immunity from encounters with the previous germs.
But the genetic shift alone is not enough to launch a pandemic. In addition, the new virus must acquire the ability to pass easily from person to person, either by random genetic change or by picking up genetic material from a previous human flu virus.
The world has had some close calls in the past few years, says Richard Webby of St. Jude’s Children’s Research Hospital in Memphis. In 1997, a bird flu in Hong Kong jumped to people, killing six. But the virus never developed the ability to pass easily from person to person, Webby said. Hong Kong authorities slaughtered 1.4 million chickens to end the threat.
Just this year, authorities became alarmed when a father and son in Hong Kong were hospitalized because of a bird flu virus, and when flu virus infected some workers in the Netherlands who had slaughtered infected chickens. The Netherlands outbreak was contained by anti-flu drugs and fast vaccination, and slaughter of the poultry, Webby said.
Scientists have been noticing a lot of flu virus in chickens and pigs globally, and a lot of variety in the strains, which is worrisome, Webby said. It’s impractical to develop vaccines against all the animal strains in case they jump to humans, and there’s no reliable way to identify the most hazardous ones, he said.
When the next pandemic shows up, experts say, it will find a population with many more vulnerable people like the elderly, infirm and those with weakened natural defenses than were living 35 years ago. It will also find a trimmed-down hospital system with fewer beds to handle a surge of patients. And while today’s anti-flu drugs will probably attack the new strain, that’s not yet clear. Supplies of the drugs and vaccines would be strained.
But still, with the improvements in health care since the last pandemic, might the next one be less serious?
“I want to believe that,” Poland said, “but we won’t know until it happens.”
A history of worldwide Influenza
The origins of influenza are unknown, but the malady is never absent for more than a few decades. The worst pandemic occurred in the early 20th century, when more than 20 million people were killed.
400 B.C.:
Hippocrates records an outbreak of a cough, followed by pneumonia and other symptoms, at Perinthus in northern Greece (now part of Turkey). Several possible identifications have been suggested, including influenza, whooping cough and diphtheria.
212 B.C.:
The historian Livy describes an infectious disease, perhaps influenza, which strikes the Roman army.
1781-'82:
Considered among the greatest manifestations of disease in history, this pandemic afflicts two-thirds of the people of Rome and three-quarters of the population of Britain. Influenza also spreads widely in North America, the West Indies and Spanish America.
1789:
A widespread epidemic hits New England, New York and Nova Scotia in the fall. Most deaths appear to come from secondary pneumonia.
1829-'32, 1836-'37:
An epidemic begins in Asia late in 1829. From there it spreads to Indonesia by January 1831. The disease also breaks out in Russia in the winter of 1830-'31 and spreads westward. By November it reaches the United States.
1889-'90:
1889-'90:
Named the Russian flu, this worldwide influenza epidemic, the most devastating to that time, begins in Central Asia in the summer of 1889, spreads north into Russia, east to China and west to Europe. It eventually strikes North America, parts of Africa and major Pacific Rim countries. By conservative estimates, 250,000 die in Europe, and the world death total is two to three times that.
1917-'19:
The Spanish flu, the most lethal influenza pandemic ever, kills more than 20 million people. More people die as a result of this flu than die during World War I. Its spread is facilitated by troop movements in the closing months of the war. Mortality rates are unusually high for flu, especially among young, otherwise healthy adults.
1957-'58:
The Asian flu starts in southwest China in February 1957, possibly having originated in 1956 in Vladivostok, Russia, then spreads throughout the Pacific. Globally it affects 10 percent to 35 percent of the population, but overall mortality is much lower than in the 1918 epidemic, about 0.25 percent.
1968-'69:
Hong Kong flu claims 700,000 lives worldwide, 34,000 in the United States.
1976:
The Swine flu, isolated in New Jersey in a young army recruit, instills fear of a new pandemic and leads to a massive influenza-immunization program. The vaccinations lead to Guillain-Barre syndrome, an ascending paralysis, in 100,000 people and kills 5 percent of those afflicted.
1986:
Avian variation of the swine flue in the Netherlands results in one severe case of pneumonia.
1988:
The Swine flu kills a pregnant woman exposed to a sick pig in Wisconsin.
1993:
Strain of the swine flu in the Netherlands sickens two children. The fathers are believed to have come in contact with infected pigs.
1995:
One adult contracts conjunctivitis in the United Kingdom after infection with the duck virus.
1997:
The Hong Kong Poultry virus infects at least 18 people, killing 6 of them.