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CHAPTER IX.

Epidemic and Endemic Malaria.

I.—DISTINCTION BETWEEN ENDEMIC AND EPIDEMIC MALARIA.

     Before going further we should clearly appreciate the importance of this "mor-
tality causing" or speaking generally "virulent" type of malaria as distinct
from endemic malaria, and realise that in the investigation of malaria in the Punjab
we have to consider not only the conditions associated with mere transmission of
malaria which resemble as will be seen those frequently described in different parts
of the world, but even more urgently to ascertain what are the causes of the pecu-
liar epidemics, which as we have seen are such a prominent feature of this pro-
vince. The most essential characteristic of the condition is the mortality with
which it is associated. Indeed to measure fulminant malaria we have at pre-
sent only one criterion, namely, the degree of mortality which results from it.

     A high degree of endemic malaria we have seen may on the contrary co-exist
with a more or less normal death rate.

     Probably with severe endemic malaria there is a certain amount of increased
mortality. But whatever the effect of endemic malaria upon mortality may be,
it is the epidemic and especially the fulminant type of the disease which most
severely affects the Punjab and which alone forces itself upon the public notice, so
as to cause comment and alarm.

     In "epidemics" in fact we see the instrument by which malaria attacks the
Punjab and possibly part explanation of the fact that the recorded death rate from
"fever" for this area, contrary to what one might have expected, is higher than
that of the more tropical and one might have thought more malarious southern
portions of India.

     When we talk of malaria ridden tracts we must know clearly what we are refer-
ring to, whether the decrease of the population is inherent in the region or due to
the chance involvement in the area of an epidemic or several epidemics follow-
ing one another. We shall see more of the relation between the two conditions
later.

II.—RELATION BETWEEN EPIDEMIC AND ENDEMIC MALARIA.

     If we investigate the frequency with which different portions of the Punjab are
affected with severe epidemics of malaria, we see at once that the western half or
comparatively rainless portion of the Punjab is relatively unaffected.

     Passing eastwards we come to a tract we have called elsewhere the Northern
Epidemic Area and which, in the forty years or so for which we have data, has