Hantaviruses are harbored by rodents and can cause lethal diseases in humans. To elucidate allometry of infection in the main hantavirus reservoir in Brazil, 246 Necromys lasiurus individuals were captured, measured and tested for the presence of hantavirus antibodies in 2008-2013. Sampling was located in four Brazilian savannah areas within a hantavirus cardiopulmonary syndrome hotspot. Seroprevalence was tested by enzyme-linked immune sorbent assays. We used correlation and multivariate analysis to understand associations between sex, age, weight, standard body measurements (ear , tail and hind foot length) and presence of external wounds between infected (n=27) and non-infected rodents (n=219). Infected rodents represented a subset of the multivariate space of non-infected rodents. Infection probability did not vary with sex, but young individuals had half of the probability of subadults/adults on presenting the infection. Interestingly, there were more subadults (n=16) infected than adults (n=9), indicating that subadults are highly prone to spread the disease. Infected rodents had weaker correlation between all measurements when compared with non-infected ones, except for correlation between hind foot and ear length; it increased from +0.38 (not infected) to +0.88 in infected rodents. Injured rodents had higher probability of infection than non-injured rodents. Thus, the main attributes related to hantaviral infection in the natural-reservoir N. lasiurus are age and the presence of external wounds. These potential quick indicators can add up to infection diagnosis and security measures in the field. Future investigations on different species should enlighten attributes associated with effective hosts of emerging infectious diseases.