“The disease in spite of all barriers penetrated into England and Wales in advance of the literature concerning it.”
The disease Flexner was describing was encephalitis lethargica, the deadly epidemic brain infection that raged around the globe between 1918 and 1930, but his point is relevant to all diseases of public-health importance, including influenza. Although the disease was first described by the French, it became known as von Economo's disease. Epidemic encephalitis roughly coincided with the influenza pandemic of 1918, the so-called Spanish 'flu, but whether the encephalitis had anything to do with the influenza we may never know. Researchers are still struggling to understand what made this virus so virulent. The story, including efforts to analyse virus recovered from 80-year-old laboratory specimens or the lungs of victims buried in the permafrost, is retold in Flu, by New York Times reporter Gina Kolata (MacMillan, 1999).
Whether this research will tell us why the influenza strain was so contagious and virulent remains to be seen. But what is certain is that the world will see another influenza A pandemic. Should the next pandemic be caused by a virus as deadly as that of 1918, the potential for disaster is greater than ever. The world's population, now more than 6 billion, is three times greater than it was in 1918. Nearly half that population now resides in urban areas, including hundreds of millions crowded into the slums and shanty towns of the developing world. With today's highly mobile populations, such an influenza strain could spread around the world in days. Another pandemic would challenge the world's public-health resources as never before.
Fortunately, WHO, working with an international network of virus laboratories and disease surveillance centres, has established a global influenza-monitoring system that has a good chance of discovering the next potentially pandemic influenza virus soon after it emerges. Every year, quietly and competently, this network goes about the business of characterising the antigenic changes of various strains and determining the best vaccines for the coming influenza season. Also in place, though yet to be tested, is the WHO plan for the Global Management and Control of Influenza Pandemics. This effort recognises that an effective response to the next pandemic will require an unprecedented marshalling of diverse resources, including public-health agencies, manufacturers, and governments and, to mobilise the public, the media.
Unfortunately, while eventsryone seems to have an instinctive idea of what an epidemic and a pandemic might be, the definitions are loose, varying from country to country, agency to agency. Last month, for example, France was reporting 861 influenza cases per 100 000 population, a figure described in WHO's Weekly Epidemiological Record for Jan 21 as “well above the epidemic threshold of 58 per 100 000”. The Swiss too seem to feel they have an epidemic. Across the Atlantic, on the other hand, the US Centers for Disease Control and Prevention believes that “this year's flu season has not been unusually severe”. Meanwhile, the UK has witnessed a confusing dispute over what an epidemic is. To the British public, which routinely reads press reports characterising a handful of cases of meningitis in one village as an epidemic, the official definition for influenza of 400 cases per 100 000 must seem apocalyptic. However, the rate last month fell short of that threshold even when the government's chief medical officer, speaking of an epidemic, factored in cases that bypass direct medical consultation. This dispute prompted government critics to charge that the term “epidemic” was being misused to cover up a serious decline in the nation's health services. Response to a future pandemic of influenza, especially if it were to carry with it complications as deadly as those seen in 1918, will demand the support and cooperation of the public. “Epidemic” may sound more professional than that old stand-by, “there's a lot of it about”. But at a time when people are becoming increasingly sceptical of the motives of public officials, the word should be reserved for crises that truly warrant the term.