90-Second Read: This small rodent is at the center of theories about the Hantavirus outbreak

Experts who study Hantaviruses say the episode highlights how little we know about these pathogens' circulation in the wild-and why more research is necessary to head off an outbreak before it begins. In a 2018 study, for instance, Escobar and colleagues identified other rodent species in Chile and Argentina that can carry Andes Hantavirus and may pose a risk to humans, including the southern big-eared mouse, the long-haired grass mouse, and olive grass mouse. In South America, for example, periods of high rainfall can create "booms" in rodent populations known as "ratadas" that have been linked to Hantavirus outbreaks, Torres Perez says. It's still unclear how, or where, the outbreak started.

Andes virus largely spreads to humans who breathe in viral particles found in rodents' feces, urine, and saliva, and is the only Hantavirus known to transmit between people. Officials suspect that the first known infected individuals of the current outbreak-a Dutch couple on the cruise who died in April after falling ill-may have been exposed to Andes virus in areas where the rat lives in South America. It's much smaller than the rats you might see scurrying around the streets of, say, New York City: It's body is often a little more than the size of a AAA battery, Escobar says, although they can be bigger. The species is also an "ecological generalist," meaning it can thrive in both forests and grasslands, and can even live near houses in rural areas.

By one estimate, nearly 10 percent of long-tailed pygmy rice rats in some areas carry the pathogen. Most of the studies that you're going to see in the literature are reactive. While the rodent appears to be the Andes virus' primary "reservoir"-that means it's most prevalent in this species-other rodents in South America can pick it up, too. Scientific American has served as an advocate for science and industry for 180 years, and right now may be the most critical moment in that two-century history.

The relationship between the virus and host is a "a co-evolutionary process," says Fernando Torres Perez, a professor at the Institute of Biology, at the Pontifical Catholic University of Valparaíso, in Chile. There has never been a more important time for us to stand up and show why science matters.