STOCKTON — The advent of television and air conditioning may have played a role, along with spraying mosquitoes, in reducing encephalitis cases in the Central Valley, two researchers say.
Encephalitis, also called sleeping sickness, reached a peak of more than 400 cases in the Sacramento and San Joaquin valleys during 1952. The disease causes headaches, high fever, stupor, disorientation, coma, tremors and, in severe cases, paralysis or death.
Mosquito abatement districts have sprayed mosquitoes faithfully for years, and there have been no further encephalitis epidemics since the 1950s. No cases have been found in humans at all since 1979.
That may be partly because people began staying indoors more often after television and air conditioning became popular and generally available in the 1950s, said Paul M. Gahlinger, assistant professor of epidemiology at San Jose State University.
He and William C. Reeves, an epidemiology professor at University of California, Berkeley, led a study of possible links between encephalitis outbreaks and changes in leisure life styles. Their findings were reported at the recent annual California Mosquito and Vector Control Assn. meeting in Stockton.
Still Found in Chickens
Presence of the virus in chickens has not declined, the researchers discovered. Still, people are not as susceptible to encephalitis because they are not outside as often as in the past, they reasoned.
"People who watch television indoors on warm summer evenings with their air conditioners on are less likely to be exposed during the peak biting period for mosquitoes that carry encephalitis," Reeves said.
A poll of 379 people in Kern County, which once had the valley's worst encephalitis rate, showed that most respondents preferred to stay inside during prime evening television hours.
The research indicated that the valley counties where television ownership is highest are the areas where encephalitis rates have been lowest in the last three decades.
The results of this study do not mean that mosquito abatement programs are not needed, but they do show how varied causes of any illness can be, Gahlinger said.
"The real value (of the research) will be that many more factors should be considered--including behavioral factors--in determining the risk of disease," Gahlinger added.