http://www.nature.com/news/2005/051121/full/051121-7.html
News
Published online: 23 November 2005; |
doi:10.1038/news051121-7
Most malaria affects 'unlucky few'
Some people are more susceptible because of their
smell or location.
Michael Hopkin
Most cases of malaria hit a relatively small
proportion of a given population, according to an
analysis of health data from sub-Sarahan Africa.
Identifying these high-risk people could lead to
better use of public-health resources, say the authors
of the study.
Just 20% of people in a given area account for 80% of
all infections, says a research group led by David
Smith of the US National Institutes of Health in
Bethesda, Maryland. The next problem is to work out
just who they are.
There are some obvious factors that make people more
susceptible, such as living in poor homes without
nets, close to stagnant ponds where mosquitoes tend to
breed, Smith says. But other factors, such as the
chemicals given off in breath, sweat and dirty linen
may also play a role that is not yet well understood.
"People often say, 'I'm one of those people that
mosquitoes love to bite'," Smith adds. "Now we've
shown that it's worth taking this biting pattern
seriously."
The analysis, which uses existing data on malaria
incidence in more than 90 populations of African
children, shows the extent of this person-to-person
variation. And the results, reported in Nature1, could
help to direct efforts to combat malaria, Smith
argues. "If we can find these people we can target
them," he says.
Weak links
Malaria currently infects some 300 million people a
year, mostly in sub-Saharan Africa. It has proven
difficult or impossible to distribute enough drugs,
vaccines and mosquito-proof bednets to everyone at
risk.
Smith argues that identifying the most vulnerable
should help to concentrate resources where they are
needed. But others argue that the best way to do this
is to target efforts at those who present themselves
with malaria, rather than searching for a mysterious
sub-section of the population who are most at risk.
The patterns spotted by Smith's group might be useful
in urban areas, says Charles Delacollette, a
coordinator in the World Health Organization's Roll
Back Malaria Department. Here, the at-risk 20% will
probably be identified as those living in poor
housing, close to known sites of mosquito breeding, he
suggests.
But in remote villages, he argues, the main problem is
simply getting supplies to the villagers at all, let
alone determining the 20% within each community who
are most at risk. "Those most at risk are those who
cannot access health services. This is where the major
problem is," he says.
Smith counters that the most effective protections
against malaria are expensive. So identifying the
people most in need of it will be important in
reducing the overall public-health burden of malaria,
he argues. "If we get these people right we'll be
protecting everyone else too."
References
Smith D. L., Dushoff J., Snow R. W.& Hay I..
Nature, 438. 492 - 495 (2005). | Article |
<http://www.nature.com/doifinder/10.1038/nature04024>
http://www.nature.com/news/2005/051121/full/051121-7.html
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