STINGRAY INJURIES

access to prIVIeS, a fall in the incidence of dysentery was to be expected after treatment of this source of infection. This hope was realized, as infections by the Shigella group were reduced in number, and the fatal cases also. Early in 1948 poliomyelitis became prevalent for the first time in the county, and in view of the known excretion of the virus in the freces it seemed worth while to try to reduce the density of infection of poliomyelitis by similar means. The presence of two ethnic groups in the county, Latin-American and Anglo-American, added to the interest of the epidemiological studies. The patients were examined in a hospital ward specially established for the study of this disease, and the work was carried out by Ralph S. Paffenbarger under the regis of the United States Department of Health, and James Watt, from the Poliomyelitis Laboratory, Baltimore. ' Population figures of the nine largest towns were checked, and rural figures estimated. Detailed data were collected by special workers so as to gain information about homes as possible source of infection. Careful definitions were drawn up to establish criteria of infection and of "probable" infections, and adequate descriptions of "contact", both direct and indirect, were accepted. These criteria were rigid, and in the cause of accuracy other possible but unproven avenues of contact were disregarded. One point of interest was noticed. During the last forty years some changes have occurred in the age-specific attack rates in the United States, the previously held figure of under five years ~f a;ge, from 9% to 12% of total population, no longer turnishing 50% to 90% of the cases with the same consistency. This reckoning, however, still held good for Hidalgo county,. no doubt owing to the relative immunity of this area durmg previous years. One question which the workers wished to solve was the relative importance of human beings and flies as vectors of the disease. Fly counts were carried out and the figures were compared between the "treated" areas and others. Relations of the fly populations were also studied in different areas. With regard to the possible human vectors contact within households and contact in the general population were compared as far. as the information was obtainable. When the evidence was examined, little was in it to suggest that flies played any significant role in spreading the epidemic. The :;. uthors admit that even in "treated" areas only a cortain proportion of the flies were killed, but the estimation of the importance of this consideration is iike the reliability of a history of human contact, very difficult to establish. An effort was also made to determine the significance of nODparalytic infections; the figures available show that the rate per 1000 of Anglo-Americans was 197 and that of the Latin-Americans 34. The authors sum up their findings by stating that fly control instituted before and continued during an outbreak failed to reduce numbers of cases or "to affect the time-course of the epidemic in cities with community-wide fly control". The number of histories obtained in which contact was established with a preceding paralytic case is suggestive of this being the mechanism of transfer. Finally they think that personal contact, directly or indirectly, played a "definitive role" in th~ spread of the epidemic. In this last study the presence of the two ethnic groups with different socio-economic conditions was helpful in the analysis.