How Wet Weather in Argentina Helped Fuel the Cruise Ship Hantavirus Outbreak

The hantavirus outbreak aboard the MV Hondius cruise vessel has created a planetary nationalist wellness crisis. But the operator of it is simply a rodent that weighs astir an ounce, and clime shifts this twelvemonth that person helped summation the likelihood of transmission.

Across the Southern Cone, researchers person agelong associated wetter years with explosive rodent colonisation booms—known locally arsenic ratadas—that tin amplify hantavirus transmission. This year’s roar reflects a broader signifier of illness outbreaks shaped by clime change, biology disruption, and a hyperconnected world.

“These are emerging diseases due to the fact that the organisation of some the reservoirs and the viruses is expanding,” says Karina Hodara, a researcher astatine the Faculty of Agronomy astatine the University of Buenos Aires who studies hantavirus ecology. “Humans question crossed continents successful a substance of hours.”

The long-tailed pygmy atom rat is the communal sanction for respective taxon that unrecorded successful Chile and Argentina that tin harbor hantavirus. Each taxon is associated with antithetic hantaviruses depending connected geography.

It’s inactive unclear wherever the archetypal passengers that got sick with the Andes microorganism contracted it. But the Patagonian long-tailed pygmy atom rat (Oligoryzomys longicaudatus), which inhabits confederate Argentina and the woods and shrublands successful Chile and weighs astir 1 ounce, is the main reservoir of the lone known hantavirus susceptible of spreading from rodents to humans and betwixt humans. This person-to-person transmission “is precisely what makes outbreaks possible,” adds Raúl González Ittig, an adept successful colonisation genetics and improvement astatine the National University of Córdoba.

But different rodents, including the Pampas long-tailed pygmy atom rat (Oligoryzomys flavescens), tin transmit the microorganism to humans. The virus’s dispersed is driven successful portion by changing ecological conditions. When nutrient becomes abundant—following events specified arsenic the wide flowering of Patagonian bamboo (Chusquea culeou) oregon periods of accrued effect accumulation from shrubs specified arsenic rosehip and blackberry—rodent populations tin grow rapidly. “They devour without limits,” Hodara says. “And past they statesman reproducing precise quickly.”

As much rodents vie much intensely for territory, food, and reproductive access, assertive encounters betwixt males increase. That, successful turn, tin summation transmission of the microorganism done bites oregon saliva. Once infected, rodents shed the microorganism into the situation done urine, feces, and saliva.

“Long-tailed pygmy atom rats are climbers and tin determination much than 2 meters precocious successful trees. That has some affirmative and antagonistic effects,” explains Isabel Gómez Villafañe, a researcher astatine the Institute of Ecology, Genetics and Evolution astatine the University of Buenos Aires. On 1 hand, contaminated urine oregon feces deposited higher up are much exposed to ultraviolet radiation, which deactivates the virus. On the different hand, successful enclosed environments—such arsenic sheds, cabins, oregon houses—the microorganism whitethorn persist longer. And arsenic radical determination done these landscapes, particularly during warmer months, interaction with contaminated surfaces becomes much likely.

Climate variability is 1 of the main factors shaping the colonisation dynamics of Oligoryzomys species. During adust years, there’s little nutrient disposable for rodents, which tin little the population, portion the other is existent successful wetter years, upping the likelihood for much viral transmission.

According to González Ittig, this is the origin that champion explains the summation successful hantavirus cases recorded since past June.

Health officials person reported 101 confirmed cases, astir concentrated successful cardinal Argentina and associated with the Lechiguanas strain of the microorganism transmitted by Oligoryzomys flavescens—double the magnitude of the erstwhile 12-month period.

“We had been coming from years of aggravated drought, and past successful 2025 a wetter rhythm began with the accomplishment of El Niño,” González Ittig says. Central Argentina saw above-average rainfall, according to the nation’s upwind service, aft years of drought. Patagonia, however, experienced a much uneven pattern, with wetter conditions successful immoderate Andean areas but persistent precipitation deficits elsewhere. Researchers accidental those shifts apt boosted vegetation maturation and expanded nutrient availability for rodents.