Success  of  Measures.  —  The  phenomenal  success  of  these
measures  in  Havana  has  already  been  referred  to,  but  the
eradication  of  the  disease  in  the  Canal  Zone  is  a  still  more
remarkable  achievement.  Havana  is  a  compactly  built,  well-
drained  city,  and  was  under  military  rule.  The  Canal  Zone
is  about  forty-five  miles  long,  with  swamps  and  streams,  many
straggling  villages  and  camps,  a  heavy  rainfall,  continuous  high
temperature,  a  constantly  changing  non-immune  population,
stupendous  engineering  works  altering  the  configuration  of
the  land,  and  a  persistent  yellow-fever  infection  for  centuries.
This  disease  had  been  the  chief  obstacle  in  the  construction
of  the  Panama  railroad,  and  it  was  the  chief  obstacle  to  the
French  in  their  canal  work.  Their  loss  by  death  from  this


398       THE  SOURCES  AND  MODES  OF  INFECTION

disease  amounted  probably  to  from  12  to  15  per  cent  per
annum.1  Sanitary  work  began  on  the  isthmus  in  February,
1905,  at  which  time  yellow-fever  cases  were  being  constantly
reported.  The  cases  soon  began  to  decrease,  and  within  a
year  the  disease  was  practically  exterminated.2  In  Rio  Ja-
neiro the  campaign  against  yellow  fever  began  in  April,  1903.
The  undertaking  was  expensive,  as  it  always  must  be  if  it  is
to  be  successful.  It  required  the  expenditure  of  $1,650,000  a
year  and  the  employment  of  thirteen  hundred  men.  Deaths
from  yellow  fever,  which  had  averaged  twelve  hundred  a
year  for  nearly  forty  years,  decreased  rapidly,  as  is  shown
by  the  following:

Year.  Deaths.
1903 584

1904 48

1905 289

1906 42

1907 39

1908 4

1909 0

In  Vera  Cruz,  which  was  another  stronghold  of  yellow
fever,  the  disease  has  been  almost  eradicated  by  the  employ-
ment of  anti-mosquito  measures.3

Filariasis.
