early January 2006, the African continent saw its first reported outbreak
of A/H5N1, the pathogenic strain of avian
flu that is now spreading quickly
in birds around the globe. The virus hit a large commercial egg farm
in Kaduna State, in northern Nigeria. In less than a month, the virus
had killed more than 40,000 chickens. Soon after, it was detected in
the countries of Niger to the north, and Cameroon to the south.
|On May 16, HSPH Dean Barry
Bloom presented a live web seminar "Bird Flu: Public Health
click here to view an archival recording.
the discovery of the deadly virus in Africa portend? To find out, the
Harvard Public Health Review spoke with the Harvard School of
Public Health's Max
Essex, the John LaPorte Given Professor of
Infectious Diseases in the Department of Immunology and Infectious
Diseases. For 20 years, Essex's team has been conducting research
on the virology, immunobiology, and molecular epidemiology of hepatitis
and HIVs in laboratories in Boston and at several sites in Africa,
especially Senegal, Tanzania, and Botswana. As someone very familiar
with the public-health
problems in resource-poor Africa, Essex has deep concerns about stemming
this new disease on the continent.
Here are his thoughts.
On the magnitude of the problem
That AH5N1 has now been found in Africa is particularly frightening.
I would think it would be appropriate for the U.S. government and
the other European Economic Community players to declare some kind
program to do more comprehensive sentinel surveillance in Africa
and see what's happening beyond the commercial farms in which
AH5N1 has been found. And that means mobilizing funds as well as
the U.S. and Western Europe, very few chickens are kept in people's
yards. In Asia, Thailand, Vietnam, and China, the number is quite a
bit higher; in Africa, it's even higher. In most villages in
Africa, people have 5 to 30 chickens running around, a few sheep or
a pig or two. It's extremely likely that AH5N1 is already present
in a lot of those chickens, at least in the regions of West Africa
around Nigeria and Cameroon. And the infection of those privately kept
is probably even more important than the infection of the 40,000-chicken
commercial flock, because they're the ones with access to the
people. In almost all the cases in Thailand, Vietnam, China, and Turkey,
to people have occurred when they've had a lot of interaction
with the chickens--killing them and being sprayed with their blood.
commercial organizations do that with machines. Villagers do that by
hand, so they're at greater risk for becoming infected.
flu in humans
In Africa, diagnosing that a villager has died from avian flu would
be a lot harder than in Turkey, Thailand, and China, for example, because
there are fewer medical experts and so, fewer chances that AH5N1 would
be suspected and investigated as a cause of death. And so I would not
in any sense rule out that people have already been infected with the
virus in Africa--even dozens of them. I think that's a very
On surveillance efforts in Africa
Surveillance of AH5N1 is poorer to begin with in Africa than in
clinical surveillance, because there are not as many medical experts,
and molecular epidemiologic surveillance, because there are not as
many people who can do lab workups or serology monitoring. Indeed,
happened in Turkey or Thailand regarding transmission to humans has
already happened in Nigeria, I don't think anyone can possibly
have noticed at the world-surveillance epidemiological level. In
Asia, a lot more
is known about the movement of the virus in the avian populations and
the number of people getting occasional infections from chickens.
virus capable of efficient human-to-human transmission
the number of infections is soon to be higher in Africa than in Asia,
of recombination events--which could lead to a virus
that could transmit efficiently from human to human--is also higher.
Yet even if that happens and many more people die, they are a lot less
likely to be noticed than in other countries.
In my opinion, the chance
that any epidemic could get a head start in the human population is
higher in Africa than other places in the world
because there is less infrastructure to detect what's going on.
There are higher rates of human illness to begin with in Africa, and
you would not be able to distinguish avian flu from HIV/AIDS and many
other illnesses unless diagnostic tests and experts were available.
HIV viruses have emerged much faster in Africa than in any other
parts of the world. There are now at least four different HIVs in Africa,
each of which has infected millions of people. Many more are rapidly
emerging as new chimeric HIVs--illustrating exactly what can happen
to bird flu AH5N1 to make it more transmissible between people.
On what can be done
The World Health Organization has sent out representatives to do surveillance
in the geographical areas with proximity to the affected commercial
flocks, and to ask questions about whether chickens are dying on family
around there. But how many people can be mobilized by WHO, and how
much effort can be extended to sample these family household chickens?
virus is likely in a lot of areas--not just in Nigeria, but wherever
there are bird flyways from Europe. In international efforts of this
type, WHO, I suspect, is the only first responder, and its budget and
expertise are limited. There isn't a huge critical mass of experts
already funded and ready to go. One of the limitations in our modern
global interaction capabilities is that virtually all the expertise
and resources are still national, rather than international. Further,
regions of the world where human expertise and resources are in shortest
supply, such as Africa, are most likely to serve as particularly fertile
ground for getting a large-scale human flu epidemic off to a robust
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