In the 1990s, with the identifi cation of hantavirus pulmonary syndrome (HPS) and the risk of occupational transmission, conservative biosafety measures in handling rodents potentially infected with hantavirus have been established for researchers in the fi eld. Recently, with the advanced knowledge about the biology and etiology of HPS and based on serological surveys for professionals who regularly handle rodents, it has been observed that the risk of contracting the disease is exceedingly low. Groups of professionals in the fi eld of zoology and ecology, among others, began to question the need for an adaptation of conservative protective measures previously published. In this context, taking into account some unintended negative and undesirable consequences during fi eldwork with the overprescription of preventative measures, in 2008, the American Society of Mammalogists provided revised guidelines for personnel working with rodents potentially infected with viruses that cause HPS in humans, considering that the level of HPS protection should be proportional to the level of risk exposure observed in many fi eld activities.