 | Figure 1
Nature Medicine
6, 729 - 731 (2000)
doi:10.1038/77438
Balancing risks on the backs of the poorAmir Attaran, Donald R. Roberts, Chris F. Curtis
& Wenceslaus L. Kilama | | | | Figure 1. Cumulative malaria cases derived from Pan-American Health Organization
data for Brazil, Colombia, Peru, Ecuador and Venezuela.
The components of the calculations include the number of blood slides examined
annually (a), number of positive slides annually (b), annual
proportion of positive slides (b/a =
c), annual population for five countries (d), baseline
annual blood examination rate (e), standardized number of slides examined
(f) and standardized number of malaria cases annually (g). Two
time periods, of high (1965−1979) and low (1980 on) house spraying are
used for comparison, as the World Health Organization de-emphasized house
spraying in 1979. e = a/100 population
(sampling effort). Using the average values of a and d over
the high spraying period (a/d)  100, yields an e
value of 2.525, which was used to standardize f for each later year:
f = 100 e d.
The value f was used to estimate g as g
= f c. Data represent the cumulative
(running total) values of g for all years. Red triangles, houses sprayed
per 1,000 population, calculated from d and the number of houses sprayed
annually in all five countries; green bars, cumulative cases. The Pan-American
Health Organization stopped publishing rates of house spraying after 1992,
although DDT use since then has been minimal (data not shown).
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