[The number of beds needed for patients with infectious diseases that require hospitalization by law]

Using a statistical model, a study was conducted on the number of beds that are needed for patients with infectious diseases who are required by law to be hospitalized.

Based on 1995 data, the incidence of such infectious diseases and the average duration of isolation of these patients in Japan were obtained. Using a Poisson distribution, the probability that the number of patients that exceeds a specific number over an average duration of hospitalization was computed in a finite population. The observation period was then extended to one year and the probability that the number of patients did not exceed a specific number during one year was calculated.

In 1995, the annual incidence of infectious diseases requiring isolation by hospitalization was 1.38 per 100,000 population and the average duration of hospital confinement was 13.8 days. The estimated patient numbers calculated based on the probability of less than 0.001 that the number of patients would not exceed a specific number were: 2 for 30,000 population, 3 for 50,000 through 100,000, 5 for 200,000 and 300,000, 5 for 400,000 and 500,000, 6 for 750,000 and 1,000,000, 8 for 2,000,000, and 10 for 3,000,000.

By using a Poisson distribution, a method was developed for estimating the number of beds that are needed for patients with infectious diseases when hospitalization was mandatory.