Projections of hazards such as these are
difficult: the likelihood of infection can depend on steps civil,
national and international health authorities may take, the preparedness
of communities depends on spraying programmes and the availability of
drugs, and the numbers at risk alter as populations grow and economies
All malaria needs is somewhere warm and
wet, and a steady supply of potential hosts. The disease was once
endemic in mild, low-lying or marshy areas of Europe (the name comes
from the Italian mal aria, or bad air).
It can be controlled by spraying, and by
public education. But it remains an enduring hazard in Africa, parts of
Asia and South America. Upland communities, however, have tended to be
But the Denver team decided to forget
about all the complex possibilities and just look at some very precise
data from 124 municipalities in Antioquia in western Colombia between
1990 and 2005, and 159 administrative units in the Debre Zeit region of
Ethiopia from 1993 to 2005.
They reasoned that a match of seasonal
temperatures and reported cases would tell them what to expect.
Sure enough, they found that during warmer
years, there were more reported cases of malaria in both countries. The
“median altitude” at which cases were registered shifted accordingly
with annual temperatures. That gave them enough information to consider
some alarming possibilities.
In a previous study, scientists predicted
that a 1°C rise in global average temperatures could bring an additional
three million cases a year in Ethiopia among children under 15. As
average temperatures rise, so will the numbers of potential victims
soar, and so will the need for investment in mitigation and insect
“With progressive global warming, malaria
will creep up the mountains and spread to new high altitude areas,” said
Menno Bouma of the London School of Hygiene and Tropical Medicine, one
of the authors.
“And because these populations lack
protective immunity, they will be particularly vulnerable.”
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