living in areas endemic for malaria (Nardin et al., 1979). It is possible that these antibodies may convey immunity to challenge, but this has not been well studied. The recent review by Miller et al. (1984) provides further detailed information on the immune response to malaria, as well as on prospects for vaccination.
Malaria can exist in any climate suitable for the anopheles mosquito. Although the highest incidence of malaria is in the tropics, temperate zones are not immune. In the past, such areas as the southern United States had very high incidences of the disease. At present, the bulk of the malaria disease burden is in sub-Saharan Africa, South Asia, Oceania, and South America (Stürchler, 1984).
It is difficult to obtain reliable information on the worldwide incidence of malaria. The World Health Organization is the major source of such information. Estimates over the past decade have been in the range of 100 to 300 million cases of malaria and 1 to 2 million malaria-related deaths annually (Lancet, 1975; Wyler, 1983). Sub-Saharan Africa is the largest endemic focus. Asia and Central and South America also have large areas where malaria is highly prevalent. It is estimated that 365 million people live in areas where malaria is highly endemic and where no specific antimalaria measures are used. Those living in areas where malaria is endemic but where some measures are used number an additional 2.217 billion. Thus, nearly half of the world’s population is at some risk (SPRTTD, 1985).
Estimates of disease rates provided by Walsh (personal communication, 1985) have been used as a starting point for disease burden calculations. In the most highly endemic areas (without control), it is presumed that all infants (birth cohort about 11 million, presuming a crude birth rate of 32 per 1,000; see Chapter 4, Table 4.1) become infected in the first year of life. In other endemic areas with some control it is assumed that 20 percent of the birth cohort (about 90 million) becomes infected in the first year of life, that is, about 14 million, for a total of 25 million infant infections each year.* An
It is possible that less than one-fifth of children in moderately endemic areas contract the disease in the first year of life because the risk in some of these areas may be relatively low. It is also likely that the estimated birth cohort for heavily endemic areas may be low since the crude birth rate of 32 per 1,000 reflects the developing world average. Many of the heavily endemic areas are in