Epidemiology of rodent bites and prediction of rat infestation in New York City.

The authors examined the epidemiology of rodent bites occurring in New York City from 1986 through 1994 to identify factors contributing to increased probability of rodent bite and rat infestation. City blocks on which a rodent bite case had been reported (n=415) and three control blocks per bite block, matched by borough and randomly selected, were compared according to demographic characteristics obtained from US Census data. Environmental variables were defined using a geographic information system to extract distances to areas potentially providing food or refuge for rats, such as parks. Borough-specific models of bite risk were generated by logistic regression using data collected from 1991 to 1994; risk values were then generated for all city blocks. Field surveys for signs of rat infestation conducted on 31 randomly selected blocks indicated a significant association between degree of infestation and predicted risk. Spatial analyses comparing neighboring blocks showed that blocks with bite cases were significantly clustered. The models based on data from previous years correctly predicted 72 percent of 53 block addresses of rodent bite cases from 1995 as being locations of high or intermediate risk. A combination of geographic and epidemiologic analyses could help investigators identify the spatial occurrence of rat infestation over a large area and might help to focus control activities.