cHeroKee
08-26-2009, 10:11 AM
Southern hemisphere flu season holds hints for us (http://timestranscript.canadaeast.co...article/772126)
Published Wednesday August 26th, 2009
Northern health experts watch, learn and plan for flu season here
TORONTO - When a new, unheralded flu virus startled the world last spring by igniting the first pandemic in four decades, public health authorities in the Northern Hemisphere knew they'd caught a bit of a break.
While the virus seems to have started its journey in this part of the world, and caused a lot more illness than one would expect throughout our summer, the pandemic didn't start in peak flu transmission season.
The first real test of how the new H1N1 virus behaved in winter conditions would fall to the Southern Hemisphere. And the countries of the North could watch, learn, plan and fast-track vaccine production.
With winter now on the wane south of the Equator, experts are sifting through the experiences of temperate countries there looking for signs of what this new virus might have in store for the fall and winter of 2009-10 in northern countries.
There are few givens with notoriously unpredictable flu viruses. Still, experts say, so far this virus has carved a path and hewed closely to it.
"By and large it's been incredibly consistent across countries," says Sonja Olsen, an epidemiologist who co-ordinates a number of emerging infectious disease programs run by the U.S. Centers for Disease Control in places like Thailand, Kenya, Guatemala and Bangladesh.
"Obviously every country has different surveillance approaches, so factoring in that you can't necessarily do direct comparisons. But I think that looking at the various aspects that we've been interested in the disease, it's strikingly similar to what we experienced in the spring."
Influenza experts at the World Health Organization are focusing on the experiences of the temperate countries -- New Zealand, Argentina, Australia, Chile and South Africa -- to assess the pandemic virus's behaviour in its first true winter. Those are also the countries with the best flu surveillance systems in that part of the world.
Flu behaves differently in tropical countries, explains Dr. Anthony Mounts, an expert with the WHO's global influenza program. In the tropics flu peaks a couple of times a year, but at neither point is there as much flu activity as is seen during a true winter wave such as Canada or the countries of Northern Europe experience.
"Winter facilitates spread of influenza for whatever reason. And that seems to be what we've seen," Mounts says from Geneva.
As it did in the North in the spring and early summer, the virus spread quickly in the parts of the Southern Hemisphere where surveillance systems are strong enough to track it.
The sole exception seemed to be South Africa, where initially seasonal flu viruses predominated. Olsen says that may have been because the virus was introduced there later, after seasonal flu activity had already begun. Whatever the reason, when swine flu took off in South Africa it spread as efficiently there as it has elsewhere.
The virus appears to have sent hoards of people to their beds, but few -- in percentage terms -- to the hospital.
The pattern seems to mirror precisely what was seen in parts of North America this spring and early summer. In the majority of cases, people had what seemed like regular flu. But in a small fraction of the infected, the virus's attack on the lungs was so severe that patients ended up in intensive-care units, fighting for their lives.
These folks were, generally speaking, decades younger than those who are hospitalized with seasonal flu. And doctors who treated them reported they were profoundly ill and enormously difficult to treat. And they stayed that way for prolonged periods, jamming ICUs.
That is the type of thing for which Northern Hemisphere countries need to be planning, Mounts says. "What's going to be the total impact on our health-care system? What do we have to be prepared for?"
In the Southern Hemisphere, care of these patients has taxed the ICU units of hospitals in areas badly hit. And in a few cases which garnered a lot of media attention in Australia, a couple of patients had to be flown to other centres to find available ventilatory care. In at least one hospital in New Zealand, elective surgery was reportedly suspended because there were no free ICU beds.
But for the most part hospitals have managed, Mounts says.
Some other things are coming into focus from study of the Southern Hemisphere winter.
The new virus appears to be crowding out the two seasonal influenza A viruses that have been circulating in recent decades.
"By and large I would say that this is now the dominant virus among influenza viruses," Olsen says. But she and others note it's too soon to say whether the other two influenza A viruses will disappear, as happened in previous pandemics.
Older adults do indeed seem to be largely spared. Though the CDC reported early in May that people over 60 might have some immunity to the new virus, some experts wondered if the paucity of older cases related more to the circles in which the virus first started circulating -- younger travellers and school-aged kids and teens -- than innate immunity.
Genetic analysis of the viruses continues to show very little change among them. While that surprises some observers, others suggest that is a sign the virus doesn't currently need to mutate -- it is having no trouble finding susceptible respiratory tracts.
So does all this suggest the virus will dole out more of the same for the Northern Hemisphere this fall and winter?
"I just don't think we can predict," Olsen says. "It's helpful to know that things have been fairly consistent. But I think we don't know."
Published Wednesday August 26th, 2009
Northern health experts watch, learn and plan for flu season here
TORONTO - When a new, unheralded flu virus startled the world last spring by igniting the first pandemic in four decades, public health authorities in the Northern Hemisphere knew they'd caught a bit of a break.
While the virus seems to have started its journey in this part of the world, and caused a lot more illness than one would expect throughout our summer, the pandemic didn't start in peak flu transmission season.
The first real test of how the new H1N1 virus behaved in winter conditions would fall to the Southern Hemisphere. And the countries of the North could watch, learn, plan and fast-track vaccine production.
With winter now on the wane south of the Equator, experts are sifting through the experiences of temperate countries there looking for signs of what this new virus might have in store for the fall and winter of 2009-10 in northern countries.
There are few givens with notoriously unpredictable flu viruses. Still, experts say, so far this virus has carved a path and hewed closely to it.
"By and large it's been incredibly consistent across countries," says Sonja Olsen, an epidemiologist who co-ordinates a number of emerging infectious disease programs run by the U.S. Centers for Disease Control in places like Thailand, Kenya, Guatemala and Bangladesh.
"Obviously every country has different surveillance approaches, so factoring in that you can't necessarily do direct comparisons. But I think that looking at the various aspects that we've been interested in the disease, it's strikingly similar to what we experienced in the spring."
Influenza experts at the World Health Organization are focusing on the experiences of the temperate countries -- New Zealand, Argentina, Australia, Chile and South Africa -- to assess the pandemic virus's behaviour in its first true winter. Those are also the countries with the best flu surveillance systems in that part of the world.
Flu behaves differently in tropical countries, explains Dr. Anthony Mounts, an expert with the WHO's global influenza program. In the tropics flu peaks a couple of times a year, but at neither point is there as much flu activity as is seen during a true winter wave such as Canada or the countries of Northern Europe experience.
"Winter facilitates spread of influenza for whatever reason. And that seems to be what we've seen," Mounts says from Geneva.
As it did in the North in the spring and early summer, the virus spread quickly in the parts of the Southern Hemisphere where surveillance systems are strong enough to track it.
The sole exception seemed to be South Africa, where initially seasonal flu viruses predominated. Olsen says that may have been because the virus was introduced there later, after seasonal flu activity had already begun. Whatever the reason, when swine flu took off in South Africa it spread as efficiently there as it has elsewhere.
The virus appears to have sent hoards of people to their beds, but few -- in percentage terms -- to the hospital.
The pattern seems to mirror precisely what was seen in parts of North America this spring and early summer. In the majority of cases, people had what seemed like regular flu. But in a small fraction of the infected, the virus's attack on the lungs was so severe that patients ended up in intensive-care units, fighting for their lives.
These folks were, generally speaking, decades younger than those who are hospitalized with seasonal flu. And doctors who treated them reported they were profoundly ill and enormously difficult to treat. And they stayed that way for prolonged periods, jamming ICUs.
That is the type of thing for which Northern Hemisphere countries need to be planning, Mounts says. "What's going to be the total impact on our health-care system? What do we have to be prepared for?"
In the Southern Hemisphere, care of these patients has taxed the ICU units of hospitals in areas badly hit. And in a few cases which garnered a lot of media attention in Australia, a couple of patients had to be flown to other centres to find available ventilatory care. In at least one hospital in New Zealand, elective surgery was reportedly suspended because there were no free ICU beds.
But for the most part hospitals have managed, Mounts says.
Some other things are coming into focus from study of the Southern Hemisphere winter.
The new virus appears to be crowding out the two seasonal influenza A viruses that have been circulating in recent decades.
"By and large I would say that this is now the dominant virus among influenza viruses," Olsen says. But she and others note it's too soon to say whether the other two influenza A viruses will disappear, as happened in previous pandemics.
Older adults do indeed seem to be largely spared. Though the CDC reported early in May that people over 60 might have some immunity to the new virus, some experts wondered if the paucity of older cases related more to the circles in which the virus first started circulating -- younger travellers and school-aged kids and teens -- than innate immunity.
Genetic analysis of the viruses continues to show very little change among them. While that surprises some observers, others suggest that is a sign the virus doesn't currently need to mutate -- it is having no trouble finding susceptible respiratory tracts.
So does all this suggest the virus will dole out more of the same for the Northern Hemisphere this fall and winter?
"I just don't think we can predict," Olsen says. "It's helpful to know that things have been fairly consistent. But I think we don't know."