It is the nature of the influenza virus to cause pandemics. There have been at least eleven in the last 300 years, and there will certainly be another one, and one after that and another after that. And it is impossible to predict whether a pandemic will be mild or lethal.
In 1997 in Hong Kong, when the H5N1 virus jumped directly from chickens to eighteen people, it killed six of them. Public health officials slaughtered hundreds of thousands of ducks, chickens and other fowl to prevent its spreading further, and the virus seemed contained. But it wasn’t. In 2004, H5N1 returned with a vengeance. Since then, it has killed hundreds of millions of birds, while several hundred million more have been culled in prevention efforts. And it has infected more than 500 human beings, killing 60 percent. The virus’s high mortality rate and memories of the 1918 influenza—the best estimates of that death toll range from thirty-five to 100 million people—got the world’s attention. Every developed nation prepared for a pandemic, as did local and regional governments and the private sector. They all based their preparations on a 1918-like scenario, but it did not come. It still could.
In March 2009, another influenza pandemic caused by a different virus did arrive, and it was nothing like the lethal one we expected. This particular H1N1 virus generated a pandemic with the lowest case mortality rate of any known outbreak in history. Nothing in the world accounted for the low death toll; it was simply luck that this pandemic virus had low lethality. The World Health Organization counts fewer than 20,000 dead worldwide, but that’s only laboratory-confirmed cases. It is impossible to know whether actual mortality was ten or even one hundred times that number.
But even the highest reasonable estimate of those killed by this latest pandemic so far—we could still see more waves of infection—still falls far below the anticipated scenario. The world assumed that preparing for a severe pandemic would allow it to adjust easily to a mild one. It was mistaken. This lesser pandemic threw the world off-balance, and very few nations have, with respect to influenza, regained their footing.
A World Under Pressure
The 2009 pandemic put the world under pressure and revealed flaws in both health systems and, more significantly, in international relations. The lessons we might learn from this past event could be of value in our ongoing war against the flu virus. But we’re still getting too many things wrong.
Virologists, epidemiologists, public health officials, even ethicists and logisticians are analyzing data from the pandemic. Based on their results, health organizations will likely adopt modest management changes. The WHO previously defined an influenza pandemic as basically any occurrence in which a new influenza virus enters the human population and passes easily between humans; it may refine that definition by adding a virulence factor, similar to the Saffir-Simpson scale for hurricanes (category 1 to category 5). Vaccine delivery systems will improve. Local hospitals will upgrade their triage practices. More fundamental changes, such as a shift in vaccine production away from chicken eggs, a technology used for more than half a century, to new production technologies were already under way before H1N1 hit and will accelerate.