This question is complex: there is no direct relationship between transmission and its consequences on health. To be able to discuss the relationships between transmission, morbidity and mortality means, at the outset, being able to distinguish: 

• The high and average endemic areas, in which transmission rates are always greater than one Anopheles mosquito bite infected by Human (PAIH), per annum.  
• The low endemic areas, in which transmission is lower than in the previous areas, with at times large inter-annual variations. 
• The epidemic areas, in which transmission is an abnormal phenomenon from which there is every chance of escape during the course of a human lifetime. 

In the areas of high transmission, a single infected bite rarely brings on a malarial attack. This is due to the gradual acquisition of immunity, a special state which provides a relatively efficacious protection against the disease, but insufficient to eliminate all the parasites. This immunity may only be acquired and maintained by multiple re-infections, on an almost permanent basis between Man and his parasite. In these areas of high transmission, it occurs in a few years at a very young age, to such an extent, that it is estimated that from five years of age, the risk of death from malaria is very low. Hence, it is easy to understand why, in a context of intense and permanent transmission, the majority of cases of morbidity and almost all the cases of mortality are concentrated among young children.  

In low endemic areas and epidemic areas, the situation is much different: a single infected bite frequently causing a malarial attack. The contact between Man and his parasite is not frequent enough for the state of immunity to be built. All age groups are concerned by malaria and the risk of death.  

In any event, no transmission rate is acceptable in terms of public health. Whatever the transmission rate, the consequences are always dramatic on all or a part of the human population.