Africa, the Infectious Continent
11/4/99
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Title: Africa, the infectious continent
Source: MSNBC
Status: Copyright 1999, contact source for permission to reprint
Date: November 4, 1999
Nov. 4 - While outbreaks of new, exotic infectious diseases - as
well as the resurgence of old killers - have surfaced all over the
globe in the past decade, no continent has been harder hit than
Africa. But with international travelers flying viruses across time
zones in a matter of hours, experts have no doubt that the emergence
of menacing microbes in one locale could bring about a worldwide
pandemic. Are infectious diseases the new Armageddon?
AFRICA'S TROPICAL climate makes it a hot zone in the most literal
sense. The continent is, to put it simply, a breeding ground for
emerging pathogens.
Add to that environmental changes - such as global warming and
destruction of the rain forests - rapid population growth and
haphazard development, and the scene is set for microbes to thrive,
international experts have warned.
Since the mid-1970s, the world has seen the emergence of 30 new
infectious diseases and the return of such killers as malaria and
cholera - many of them originating in the African continent, said
Paul Epstein, associate director of the Center for Health and Global
Environment at Harvard Medical School.
And in the past few years, floods and droughts brought on by global
warming have exacerbated the situation, he said.
"Extreme weather creates conditions conducive to outbreaks of
infectious diseases," Epstein said. Heavy rains, for example, provide
new breeding sites for the mosquitoes that carry malaria, dengue
fever and other disease, while contaminating drinking water. Drought,
on the other hand, fuels fires that, in turn, spark respiratory ills,
even meningitis.
When illness does strike Africa, a poor infrastructure - marked by
poverty, malnutrition, crowded living conditions, limited health care
and an unstable political climate - permits disease to spread
undaunted.
MANMADE PROBLEM
It's the manmade aspect of the problem that so perturbs the experts.
"These new pathogens didn't come in on a tail of a comet," said Dr.
David Heymann, executive director of the World Health Organization's
Program on Communicable Diseases in Geneva, Switzerland. "They're
lurking in animals. But by disrupting nature, we have unleashed them
onto ourselves."
The destruction of the rain forests, for example, may be partly to
blame for clusters of killer outbreaks - ranging from feverish
malaria to hemorrhagic Ebola.
When trees are cut down, pools of infested water are left exposed in
the forest, Heymann said. "What we have done is set up new breeding
grounds for mosquitoes that can carry disease such as malaria."
Dr. Anne Marie Kimball, an expert in infectious disease epidemiology
at the University of Washington in Seattle, blames deforestation for
recent Ebola outbreaks. As people penetrate the forest in search of
firewood, they can be exposed to the virus, which might otherwise
have been relatively contained, she said.
Destroying the rain forests also has led to a loss of wildlife that
protects against infectious diseases, said Epstein. "As coyotes,
snakes and other predators that normally prey upon disease-carrying
rodents and mosquitoes are killed off by man in his hunt for more
wood, for example, so is our natural buffer against plague and
malaria," he said.
"A hearty forest stocked with birds and a healthy lake stocked with
fish are important in controlling mosquitoes," he said, which may in
part explain the resurgence of such diseases as yellow fever and
malaria - the latter all but wiped out several decades ago.
Cutting down the forest can sometimes change the mice population from
forest to field mice, Epstein added, which can bring about new
viruses such as one responsible for a deadly fever in Bolivia.
"While this has yet to happen in Africa, there is every reason to
believe it can - and will - if steps are not taken," he said.
GLOBAL WARMING
Several aspects of climate change, all related to global warming, are
contributing the emergence of new diseases and the resurgence of
others, the experts say.
Warming itself is allowing malaria to spread to higher altitudes,
Kimball said, noting that the mosquitoes that carry the disease to
humans can survive only at milder temperatures. Once confined to
lower areas, the skin-piercing insects are now able to flourish in
the African highlands of Kenya.
The outbreaks have been devastating, Epstein said. With poor access
to health care, many residents were sickened and killed as malaria
swept through several villages.
El Nino-related extreme weather events also brought flooding to the
Horn of Africa, chiefly Kenya and Tanzania, he said, adding that in
1997-1998, the area was besieged with four times as much flooding as
normal. The results: huge clusters of mosquito-borne malaria and Rift
Valley fever as well as an epidemic of the water-borne disease
cholera.
The big surprise, Epstein said, are the fires brought about by recent
droughts - "something we weren't even thinking about a year ago."
The fires bring haze, choking, air particulates and respiratory ills.
Membranes dry, making residents susceptible to deadly meningitis.
There's also the impact on an already shattered economy. Due to Rift
Valley fever, which strikes cattle as well as humans for example,
Africans couldn't export livestock, Epstein said. Cholera-infested
waters limited the sale of fish.
"We knew of the link between climate and infectious disease as early
as the 1920s," Epstein said, "but people put blinders on. And now we
are paying the price."
A GLOBAL PROBLEM
While the term Hot Zone may conjure up images of suited-up medical
detectives working in containment zones to stop a deadly virus at its
source, nothing could be further from reality, the experts say. Each
killer microbe has the potential to make a lethal journey across the
globe, carried by migratory birds, international travelers or traded
goods.
"Africa' problem is not its own," Epstein said, the West Nile-like
virus' recent debut in New York being an important case in point.
While scientists are still mystified as to exactly how the microbe
made its way halfway across the world, he said, "What we can be sure
of is that the environmental and social conditions in Africa affect
emerging diseases throughout the globe."
Like West Nile-like fever, mosquito-borne dengue fever had been
confined to the tropical zones for years, Kimball said, making "an
outbreak in Texas earlier this year as scary as it is intriguing."
It appears "we're seeing a harbinger of what you can get as vectors
move worldwide," she said.
INSET
What should we be doing?
Stopping infectious diseases early - at their source - is crucial to
preventing a worldwide pandemic. Harvard's Paul Epstein suggests
these steps:
Set up better surveillance and response capabilities.
Create a Health Early Warning System to track climatic changes that
"could be conducive" to disease outbreaks.
With early warning, do public health interventions that are timely
and environmentally friendly.
Stop deforestation as it now exists.
Develop cleaner, more efficient energy sources.
Establish an international center to fund all these changes.
Estimated cost: several billion dollars a year.
Other unexplained outbreaks of infectious disease may be due to
mosquitoes hitching a ride on a plane, Kimball said. The insects can
survive in the wheel wells of aircraft, even at 40,000 feet. So if
mosquitoes set up shop while a plane is grounded in Africa, they'll
land overseas with the baggage and passengers, causing previously
unseen disease, such as recently happened in Belgium.
Travel also allows the mixing of different microbial strains when
people come together, Kimball said. The new strains are often not
just deadlier, but also may be resistant to the drugs usually used to
eradicate them.
"The world is so intertwined that a problem in one place today will
be a problem in another place tomorrow," she said. "Infectious
diseases are giving us a wake-up call to create a global community."
If we don't, the experts say, we may indeed be facing the new
Armageddon.