Update 4/30/09, 2 p.m.: This post is getting a lot of hits; I’d like to suggest that your next stop be Effect Measure at Science Blogs, which I’ve found to have the most valuable current analysis of the public health ramifications of the swine flu threat. Also, in the post below I criticize WHO for not moving up to phase 5 quickly enough; they’ve since rectified this.
Don’t panic, says the White House. Don’t panic, says the CDC. Don’t panic, says the WHO.
I don’t want them to panic either, but the people at those agencies had better be worried sick about the emerging swine flu. While the unknowns still overshadow the knowns, there’s one very troubling development that suggests why our government and public health authorities should be treating the swine flu as a far, far greater threat than 9/11 ever was.
Buried deep in a New York Times report is this nugget of information:
In each year’s flu season, most deaths are in infants and the aged, but none of the first ones in Mexico were in people over 60 or under 3 years old, a W.H.O. spokeswoman said. When a new virus emerges, deaths may occur in healthy adults who mount the strongest immune reactions. Their own defenses — inflammation and leaking fluid in lung cells — can essentially drown them from inside. [My emphasis.]
I don’t hold a degree in public health or epidemiology, but as a historian of medicine who’s familiar with the 1918 flu, I know that this is very, very alarming news. (And since I’m not a public health expert whose job entails keeping people calm, I feel free to speak bluntly about it.)
In 1918/19, the mortality pattern was exactly as the WHO describes. Historian John M. Barry describes this pattern in The Great Influenza: The Epic Story of the Deadliest Plague In History, as does Gina Kolata in her well-researched New York Times piece from 2006:
It was the worst infectious disease epidemic ever, killing more Americans in just a few months than died in World War I, World War II, the Korean War and the Vietnam Wars combined. Unlike most flu strains, which kill predominantly the very old and the very young, this one — a bird flu, as it turns out — struck young adults in their 20’s, 30’s and 40’s, leaving children orphaned and families without wage earners.
To the best of my understanding, the reason less-novel flu viruses don’t provoke such deadly immune responses is that by adulthood, most of us have encountered enough flu viruses that we have some partial immunity to the average new mutations. There’s no need for our immune system to go into overdrive. When a radically new mutation pops up, however, our immune system resorts to the nuclear option. An otherwise healthy young person’s lungs can be destroyed in the course of the resulting inflammatory process – a cytokine storm, if you want the technical term. (Here’s an accessible description of how this works in bird flu; if the swine flu deaths are indeed due to cytokine storm, as seems likely, the mechanism would be similar.) Ironically, healthy young adults are the most vulnerable, because their immune systems are the most robust.
So this mortality pattern plus the other data available so far suggest several conclusions:
- We really are seeing a novel virus.
- It’s at least moderately deadly. However, its virulence could be variable, since the U.S. has seen milder cases than Mexico, and the less extreme cases in Mexico may be flying under the radar. Remember, though, that a virus can mutate to become more or less virulent during the course of an oubreak.
- It is transmitted from human-to-human. It appears much more contagious than SARS or the bird flus that epidemiologists have tracked in recent years.
- It has shown up in far-flung parts of North America and Europe. Today, we learned that the swine flu has turned up in Lorain County, Ohio – not quite my neck of the woods, but way too close for comfort. (The infected boy is recovering well, but his school is closed in hopes of containing the outbreak.)
The only reason this swine flu is not being labeled a pandemic is because it’s not widespread enough. Not yet. Give it a week.
Here’s one example of where exhorting people to stay calm seems to be trumping the actual science. Technically we ought to be at phase 5 of pandemic preparedness – one notch short of a full-blown pandemic – if you look at this WHO graph. Officially, we’re at phase 4, but that doesn’t square with the WHO definition:
Phase 5 is characterized by human-to-human spread of the virus into at least two countries in one WHO region. While most countries will not be affected at this stage, the declaration of Phase 5 is a strong signal that a pandemic is imminent and that the time to finalize the organization, communication, and implementation of the planned mitigation measures is short.
The only reason not to panic is because losing it would make our response even less effectual. I’ve always admired Obama’s calm; his unflappability is one of his most attractive and reassuring traits. But I hope our decision-makers are at least a little scared, because so far, complacency has not concentrated anyone’s mind. Nor has it funneled adequate dollars to the fight against flu. Republicans actually fought to keep flu funding out of the stimulus – gee, thanks! (h/t Pudentilla at Skippy the Bush Kangaroo) Perhaps more damningly, eight years of GOP veto power have left us only marginally more prepared than were were when the anthrax attacks redefined public health as a national security issue!
It’s already a few years too late for the kind of preparation we would have needed: enough doses of antivirals to rein in a true pandemic, and a rapid-response system for developing, producing, and distributing a vaccine. But we need to recognize that the swine flu is poised to create a global emergency. We need to find the resources to fast-track a vaccine. How is it that we can find a trillion bucks to prop up the banks, yet we only have two labs in North America capable of identifying this vaccine – one in Atlanta, the other in Winnipeg? (This is being rectified, but it too will take time.)
Another lesson from 1918: The virus mutated some months into the pandemic and became radically more virulent in the fall of 1918, just when the world was hoping for a respite. In the end it killed somewhere between 20 and 100 million people. Every week of further delay in creating a vaccine for this new flu could cost thousands or even millions of lives.