To investigate the possibility that the cats density, the sex-ratio, the number of males or the mean age of cats within the population may act as risk factors influencing the disease transmission rate, we performed a statistical analysis of the data using the sexuallystructured SI model. Which population characteristics correlate with large FIV prevalence and so explain, in part, the variability in FIV prevalence? We found no such factors, except for mean ages. Interestingly, these ages have a negative effect on FIV prevalence in females, despite the accumulation of cases that occurs with age. One possible explanation is that the presence of older territorial males in some populations ensures greater social stability, which decreases the rate of at-risk (mating) contacts. Reversely, a negative correlation between FIV prevalence and age of cats could be due to the additional mortality induced by the virus. However, considering the weak impact of the infection on the lifeexpectancy of individuals, this explanation seems rather implausible to us.