Mosquitoes are zoophilic (feed on animals - vertebrate hosts) -
female mosquitoes get infected after feeding on viremia hosts.
After 9-12 days, incubation period - mosquitoes transmit disease
to other vertebrate hosts. The average life of Culex mosquito is 21 days.
Culex can fly over long distances of 4-5 kms. Epidemics offur during monsoon
and post monsoon period because the vector density is high. However, in endemic
areas, sporadic cases may occur throughout the year.
JE in man :
Incubation period : 5 - 15 days.
All individuals bitten by infected mosquitoes do not suffer from the disease.
Ration of overt disease to in apparent infection = 1: 200 to 1: 1000.
Thus JE follows the pattern of iceberg phenomenon of disease i.e. the cases
seen represent only a few individuals while those suffering from in apparent
infections are many and are not approached by health functionaries.
