Though occupying only one-tenth of a square mile of the 50 square mile Bellflower Health Area of Los Angeles County, California, the 712-unit, low rent Carmelitos Housing Project at Long Beach, between 1956 and 1959 had 20 to 39% of all the cases of infectious hepatitis in the area. In 1960 the incidence of this infection dropped at the housing project to 6.6%, in 1961 to 3.6% and so far in 1962 to 0.0 per cent, while at the same time the incidence has been rising everywhere else in Los Angeles County. It was found that the drop in incidence of this disease occurred concurrently with an approximate 70% drop in infestations of German, brown-banded and oriental cockroaches; the latter having been the result of a concentrated control program utilizing the new silica aerogel insecticide, Dri-Die 67.
The cockroaches' unsanitary habits, general distribution and year-round prevalence coupled with the finding of poliomyelitis virus in three wild-caught domiciliary species of cockroaches and the successful laboratory transmissions of a number of viral infections to cockroaches makes it seem far more plausible that the cockroach is capable of acting as a vector of infectious hepatitis, or other viruses, than previous evidence indicated. Therefore, it is hoped that the findings at the Carmelitos Housing Project will not only prove interesting to other investigators, but of sufficient interest to prompt them, also, to further investigate the role of cockroaches in the transmission of infectious hepatitis and other diseases.