For most hantavirus strains, transmission is straightforward: you must come into direct contact with an infected rodent or its droppings, urine, or saliva, most commonly by inhaling aerosolized particles in enclosed or dusty environments. This might happen when cleaning out a barn, cabin, or garage, or when working or camping in areas with heavy rodent activity.

Hantavirus is not known to spread through person-to-person contact with one exception, the Andes Virus strain (ANDV). Fortunately, this strain is not transmitted easily through respiratory droplets the way COVID spreads, but usually requires close contact with an infected person. Close contact typically involves prolonged contact in a closed space, such as sleeping in the same bed or sitting directly next to an infected person on a long car or bus ride. It can also be spread by touching something an infected person recently touched and then touching your nose or mouth, or by sharing food, using the same drinking straws, or sharing eating utensils with an infected person. In one study from a prior outbreak in Argentina, among household contacts of infected persons the risk of contracting the disease was 17.6% among intimate partners, and only 1.2% among other household contacts.

ANDV is most contagious just before and during the febrile prodrome period, when viral loads are highest.  Based on studies from past outbreaks in Argentina, transmission mainly occurred at a time when the infected person was quite ill, with symptoms such as fevers, body aches, and malaise.