Via STAT, Helen Branswell writes a must-read: The last flu pandemic was a 'quiet killer.' Why we can't predict the next one. This brings back a lot of memories. Excerpt:
The cryptic phone call came on a Monday. The Centers for Disease Control and Prevention was holding an important teleconference for a few reporters. I should dial in.
When the time came, just a handful of reporters were on the line. Also there: the CDC’s top flu experts. They sounded worried.
Two unrelated children from southern California had tested positive for flu infections caused by viruses that normally sicken pigs. This could have been a fluke, but from the unusual nature of the call and from the tension in the voices of the experts, it was clear that the CDC officials thought it might be something else: an influenza pandemic.
That teleconference took place on April 20, 2009. Over the next seven weeks it became apparent that any fears they had had been well-founded.
On June 11, 2009 — 10 years ago today — the World Health Organization declared that the swine flu virus we now simply call H1N1 had indeed triggered a pandemic, the first time in four decades a new flu virus had emerged and was triggering wide-scale illness around the globe.
Since it started circulating in the spring of 2009, H1N1 has infected about 100 million Americans, killing about 75,000 and sending 936,000 to the hospital, the CDC estimates. Another virus, H3N2, is responsible for more infections, but “in terms of the severity, H1 is kind of this quiet killer,” said Dr. Daniel Jernigan, head the CDC’s flu division.
In the hands of Hollywood, pandemics tend to be of the one-size-fits-all variety. They unleash massive chaos and spread at lightning speed, as health officials in hooded biohazard suits rush to distribute vaccinations. And in real life, flu pandemics, which tend to strike only a few times each century, could be that terrifying. But, a decade onward, the experience of H1N1 is a reminder that it’s impossible to know from the get-go how a pandemic will play out.
Science currently has no way to predict when pandemics will occur. The fact that there were 41 years between the 1968 pandemic — known as the Hong Kong flu — and the 2009 pandemic doesn’t mean the next will take another 30 years or so to materialize. There is no pattern; flu pandemics happen when they happen, and pandemic planning is ever ongoing.
In the case of H1N1, the public health world was steeling itself for a potentially catastrophic outbreak. Just six years earlier, officials began to respond to a very dangerous bird flu virus called H5N1, first in Southeast Asia and then beyond. It was deadly to chickens and other poultry but — and this was unusual — it was also occasionally infecting people. When it did, the outcome was sobering: More than half of people known to have been infected with the virus died from the infection.
The number of people infected with H5N1 was small, but it stoked fears that this fearsome flu might be readying itself to cause a pandemic. In its place, however, arrived H1N1.
It was distantly related to other H1N1 viruses that had circulated among people for most of the 20th century. In fact, pigs acquired H1N1 decades before from people. But this new virus had evolved in a way that helped it unlock the mysteries of the human respiratory tract and sicken people.
Fortunately, though the infection could be severe, it was not devastating in most cases. A study published in 2013 suggested between 123,000 and 200,000 people globally may have died as a result of the 2009 H1N1 pandemic.
This was certainly not nothing. But it was also not what people had feared would be in store, and it was a substantially lower death toll than was seen in the 1957 and 1968 pandemics, which each killed about 1 million people at a time of lower global populations. In fact, the H1N1 death toll was lower than the global death toll for typical flu seasons, as estimated by the WHO.
But just looking at the number of deaths masks the full impact of the pandemic, because the people who died were younger than those influenza normally claims. (The elderly, whose immune systems had seen viruses similar to this one long ago, weathered the pandemic pretty well.) A group of researchers who analyzed the deaths based on years of life lost concluded the pandemic’s toll in the United States was at least as bad as an average H3N2 flu season and potentially as severe as the 1968 pandemic.
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