25 April 2009

For World Malaria Day

From October 2, 2008

Malarial epidemiology data

(R. Carter and K. Mendis. Evolutionary and historical aspects of the burden of malaria. Clinical Microbiological Reviews, 2002. 15(4): p. 564 – 594)

Mortality (M/year)          1930       1975       2000

Americas                             0.1          <0.01>

S Asia + Middle East        2.6          0.1          0.1

China + NE Asia                 0.5          0.2          0.0

Africa                                    0.2          0.3          0.9

                                                3.4          0.6          1.0


This little table.. better shown as a graph (sorry) highlights some fascinating facts about the history of malaria. Pre the WHO-precursor DDT spraying programs starting in the 40s, malaria mortality stood at ~3.4M/year with ¾ of cases occurring in S Asia/ Middle East. From the peak in 1930 to 1975 we saw a drastic reduction in global malaria (something I never knew) down to 1M cases per year, the lion’s share of this reduction comprising the near eradication in S Asia / Middle East. (I wonder what the role of the US military activity in the region plays in this story?) China and environs also saw > 50% reduction over the same period. In per capita terms this decrease is orders of magnitude larger, i.e. this incidence of global malaria has been massively reduced. Unfortunately, just as with many other socioeconomic factors, the trend reversed in Africa during this time, with mortality rising by a factor of 5.

Unfortunately this data, although informative, can be non-instructive in terms of suggesting possible explanations as it is not quoted on a per capita basis – according to the World Bank, sub Saharan African population has doubled since the 60s. It also does not give any information on change in infection rate. An often cited reason for the increase is increased drug/insecticide resistance. However, at this stage I cannot see why this problem would be limited to Africa. Of course many other factors are proposed for Africa including weakening control programs, deteriorating primary health care and humanitarian crises in endemic areas.

So, a dangerously rough estimate of increase in per capita mortality for Africa would be something in the region of a factor ~ 2.5 since 1930 while the rest of the planet has drastically reduced its occurrence. Looking at it like this, it is not surprising that something serious is finally being done to combat this regional problem, although still shamefully late.

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