Like catastrophic flooding in New Orleans, an influenza pandemic is not a matter of if, but a matter of when and how bad. Fortunately, John M. Barry has written books about both. Until the definitive story of Katrina is told, Rising Tide, Barry’s book on the 1927 Mississippi River flooding that left some parts of the Delta a 100-mile-wide swathe of water, will stand as the classic work on power and high water and the Crescent City.
The inevitability of floods in New Orleans is a matter of geography; the inevitability of a flu pandemic is a matter of genetics. The natural reservoir for influenza viruses is in birds.
Massive exposure to an avian virus can infect man directly, but an avian virus cannot go from person to person. It cannot, that is, unless it first changes, unless it first adapts to humans.
This happens rarely, but it does happen. The virus may also go through an intermediary mammal, especially swine, and jump from swine to man. Whenever a new variant of the influenza virus does adapt to humans, it will threaten to spread rapidly across the world. It will threaten a pandemic. — The Great Influenza, p. 102
The first question about a species-jumping influenza is how virulent it is. H5N1, one of the current avian variations — the letters and numbers refer to variations in the proteins that allow virueses to bond to cells — has been worrying observers because the disease it causes in birds has had fatality rates of up to 100 percent.
By comparison, the 1918 virus, the most pathological pandemic known, had a global fatality rate of 5 percent to 10 percent. This was much higher in some populations that had had virtually no prior exposure to influenzas, but even the lower figure was sufficient to kill probably more than 50 million people globally. Because it killed so many younger people, the 1918 influenza reduced statistical life expectancy in the United States by 10 years.
Influenza is a particular problem for two reasons: its fast rate of mutation and the gap between infection and symptoms.
Since the 1918 pandemic, many lessons have been learned. The top one is monitoring. There is a global system for monitoring flu outbreaks and watching for new strains. This is what brings the annual flu shots, which are the best guess about the winter’s dominant strain and give a certain amount of immunity. But flu’s ability to mutate rapidly can mean that the several months still required to make a vaccine are too long to provide relief.
A person who shows flu symptoms has had the virus for some time — days, even — and has been shedding virus all the time. Influenza can persist on hard surfaces much longer than, for instance, SARS virus. So containing an outbreak through quarantine is much harder. The most effective preventative measure at the moment is slaughtering animals before the new strain can make the jump to humans. This was done for H5N1 in Hong Kong in 1997 and in the Low Countries and Germany in 2003 for H7N7.
But a pandemic really is only a matter of time: there were at least three and possibly six in Europe in the 18th century; at least four in the 19th; and three in the 20th. Chances are very good, though, that the next one will not be as lethal as 1918. Those of us old enough to remember the “swine flu” scare of the late 1970s will have heard this before. That disease did not live up to the hype, which is just as well. Because it really does seem to be a matter of chance and mutation as to how lethal the disease will be.
On the other hand, there are social conditions that affect outcomes, too. One of the reasons 1918 was so bad is that wartime conditions in Europe offered unusually dense concentrations of people, mixing endemic diseases from many different areas. Wartime privations also weakened immune systems; when flu struck, secondary infections found the going that much easier.
Finally, secrecy contributed to both the spread of disease and the ineffectiveness of public health measures. Newspapers in the United States, under extreme pressure not to undermine morale, did not report the full danger. Local governments lied about the disease, and higher levels of government subordinated the fight against the flu to the war. All of these actions and inactions made the casualty level higher than necessary.
In today’s world, southeasrn Asia is one of the areas where a species jump is most likely to happen. Closed societies, repressive or ineffective governments and a willingness to whitewash events all add to the overall danger.
The book does much more than tell the story of the disease. It begins at a time when medicine in America was little more than quackery, and any doctor who wanted to be scientifically trained had to travel to Europe. The founding of the Johns Hopkins University was the decisive step that launched graduate education in America (what the Brits call post-graduate study) and eventually gave the world institutions like today’s Harvard and MIT. Barry tells the story of the men who fought those battles. He also captures a sense of how medical science moves forward, in normal times and under the great stress of an epidemic. And finally, almost as a coda, he tells how it was discovered that DNA carries genes, who made that discovery and what it has to do with the great pandemic of 1918.