Nature of epidemic and method of infection.

201

in the immediate neighbourhood of a house that is occupied
by anyone who is suffering from the disease. During the early
rainless cold-weather months, when the ground is dried up,
the germs which have reached it will lie dormant; and as those
who have the disease so often lose their fever at this time of
the year, the opportunities of direct infection through the air
will be also less than at any other time and new infections will
be at a minimum. As soon, however, as the first few inches of
rain fall, as usually occurs in Assam in April, and sometimes
even in March, then the ground will once more become moist
and warm, and the conditions will become most favourable for
the multiplication and escape into the air of the temporarily
dormant germs, new infections will again become common, and
the ordinary outbreak of the rainy season will recur. When
this has gone on for some five or six years in any place, a
large number of the inhabitants will have died of the disease,
while others may have had a slight attack which is not distin-
guishable from ordinary malarial fever, but which protects from a
more serious one, while the rest are insusceptible to the disease
or have not come into sufficiently intimate contact with infected
persons to get it, and so the epidemic fever declines. The
fact that the later cases last a much longer time before they
are fatal than the earlier ones, while more of them recover,
shows that the most susceptible die first, and later those who
have more power of resistance succumb, or in other words, the
disease loses its power of attacking the surviving inhabitants
of the place, and so it gradually dies out. Whether it leaves
the place or district more unhealthy than it was before is very
difficult to say. There is also evidence to show that a site
which has been deserted on account of the fatality of this
epidemic, may yet be safely inhabited by the people who had
previously deserted it, after it has been unoccupied for some
years, for this is recorded to have taken place at the foot of
the Garo Hills, in the very part where the Deputy Commis-
sioner of the district was subsequently unable to find a single
case of the disease. This indicates that the intensified germs

2 D