Here the epidemic data of HIV/AIDS in three European countries: France, the Western part of Germany (i.e., the former Western Germany) and the United Kingdom (UK) are investigated [23] . Figure 2A shows the yearly incidence in these countries from 1976-2000. During the observation period, a total of 23,243, 13,126 and 11,491 AIDS cases were diagnosed in France, Western Germany and the UK, respectively. Although the time of HIV infection is not directly observable, the HIV incidence has been estimated by employing a back-calculation technique and using the AIDS incidence and the incubation period distribution of AIDS [23] . The present study does not discuss the details of back-calculation, but explanatory guides can be found elsewhere [24] [25] [26] . Figure 2B shows the enlarged HIV incidence curve during the initial phase of an epidemic. The peak incidence was observed in 1982 for Western Germany and 1983 for France and the UK. In the following, the time period from 1976 up to one year prior to the peak incidence is taken as the early growth phase. For the purpose of an exposition of the proposed method, the HIV incidence is assumed to have been in a single homogeneously-mixing population. 