while the months with the heaviest rainfalls were February
and March.
Under the local meteorological conditions, A. aegypti
needs 11±12 days to develop from egg to adult (National
Health Foundation, unpublished data). Thus, a period of
3 months from the onset of rainfall is long enough for
several complete life cycles of the vector and for building
up suf®cient transmission potential to cause an outbreak.
The epidemic in favela Serviluz ®ts into this pattern.
During the case±control study, we found a house with an
open water tank containing many larvae on the roof. The
house is adjacent to that of the index case at the bottom of