Pandemic preparations in place
25 October 2002 18:42 GMT
by Julie Clayton
Malta - There's no doubt in the minds of researchers who
attended this week's
First European Influenza Conference here: the emergence of a
new strain of flu virus that could sweep across the globe killing
millions is going to happen - sometime.
The conference marked the 10th anniversary of the European
Scientific Working Group on Influenza (ESWI), which has seen its
role change dramatically from focusing on basic research to making
demands for European-level preparedness for the next pandemic.
Flu experts across Europe have been working overtime to give
decision-makers in Europe and the rest of world a wake-up call to
"always expect the unexpected" when it comes to the influenza
virus. The infection's impact, they warn, is likely to be far
greater than any bioterrorist attack.
Unable to predict when the next pandemic will occur,
researchers believe they can draw many useful lessons from past
outbreaks, particularly by studying the genes carried by the 1918
"Spanish flu" pandemic strain, which killed 50 million people
worldwide, and the 1997 Hong Kong outbreak which killed six. At
least one of these - the NS1 gene, may have some effects in common
with other highly virulent pathogens, including the Ebola and
Lassa fever viruses.
Surveillance experts attending the meeting wasted no time
dispelling some of the great flu myths. First of all, on a global
scale, it does not only happen in wintertime - flu is a year-round
phenomenon. There are major peaks of incidence in the winter
months in the Northern and Southern hemispheres, but it is at
relatively constant levels year-round in the tropics. And, as John
Oxford, professor of virology at Queen Mary College, London,
notes, the great 1918 pandemic first emerged in Europe in the
summer month of June.
Year-round surveillance is therefore the only way to gain any
advanced warning to individual nations about the nature of
circulating viruses. In particular, information about the disease,
and the viruses causing it, needs to be brought together, for the
most effective vaccine recommendations to be made.
Another myth is that experts should only look to South East
Asia - China and Hong Kong - as the source of the next pandemic.
Indeed, an outbreak could occur anywhere, including Africa and the
Middle East.
But China and Hong Kong continue to provide invaluable lessons.
Here, many people are in contact with live birds, particularly
chickens and ducks, at poultry farms and live bird markets. The
1997 Hong Kong outbreak shocked flu experts by demonstrating, for
the first time, that flu viruses could jump the species barrier
directly from birds to humans. Until this happened, attention had
focused on pigs as the "mixing vessel" for avian and mammalian
viruses to re-assort before infecting human hosts.
But as Albert Osterhaus, president of the European Scientific
Working Group on Influenza highlighted, the natural reservoirs are
more likely to be migratory birds and waterfowl rather than
domesticated animals. These include gulls, ducks, and geese, which
carry the viruses, often without ill effect, in their
gastrointestinal tracts. Their droppings can fall not only on
land, but also into seas, rivers, and lakes, to form what
Osterhaus calls a "poop soup" capable of infecting aquatic
mammals, too - including seals.
Yet another myth is that protection against flu depends
entirely on antibodies. Cell-mediated immunity, including CD8
killer T cells, and the first line defenses of the innate immune
system, are also likely to play an important, though relatively
unexplored role. New live vaccines now in the pipeline are
intended to trigger this type of response.
Meanwhile, conventional flu vaccines contain inactivated
viruses that trigger antibodies. But unless manufacturers switch
to more rapid production methods or find ways to make existing
preparations stretch further, delegates heard, vaccines will not
be available soon enough, or in sufficient quantity, to cope.
The arrival of new antiviral drugs on the market, however,
promises an effective treatment for infected individuals, agreed
scientists and clinicians attending the meeting. These are
suitable for the regular flu epidemics that strike all the time,
but they also provide the first opportunity for nations to build
up efficacy in advance of the next big one.
By contrast with the victims of last century's 1918, 1957, and
1968 pandemics, those affected by the next one, "will not go
quietly," concluded Oxford.
Picture caption:
In background: Photomicrograph of Hemophilus influenzae,
CDC.
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