Argentine authorities trap rats to hunt for source of deadly hantavirus outbreak

Argentine investigators searching for the source of a deadly hantavirus outbreak on a cruise that set sail last month were trapping rodents in the forests surrounding the southernmost city of Ushuaia on Tuesday, with the aim of detecting the possible presence of the rat-borne virus in an area previously thought unaffected.

The scientists, wearing bright blue gloves and surgical masks, checked the 150 box traps they had set out the previous night, dropping dead rats into black plastic bags they hoisted into pickup trucks bound for a makeshift lab where they said they'd take blood.

Tuesday's rat-trapping marks the start of fieldwork within Argentina's wider investigation into the origin of the contagion that struck the MV Hondius, killing three people, sickening several others, including one Canadian, and setting off a global scramble to trace passengers and their close contacts.

Argentine investigators trudging through mud to retrieve the dead rats declined to speak to journalists about their work.

The state-backed Malbrán Institute, Argentina's leading research centre for infectious diseases, said the team would repeat the routine for the next three days before returning with the samples to the institute's main Buenos Aires laboratory to test for hantavirus.

Testing could take up to one month, but officials were tight-lipped about further details.

"They were able to capture what was expected," said Martín Alfaro, the spokesperson for the local health ministry of Tierra del Fuego.

WATCH | Canadian aboard cruise ship tests positive for hantavirus:

Canada's first positive case of the Andes strain of the hantavirus has been confirmed in B.C. Infectious disease specialist Dr. Srinivas Murthy describes the virus's severity as 'scary,' but he says South America has successfully managed it for decades.

The effort comes almost two weeks after the Argentine Health Ministry first announced it would send the team from the Malbrán Institute to Ushuaia.

The popular tourism destination where the cruise departed — famed for its location at the "end of the world" — serves as the main gateway to the Antarctic.

The hantavirus has never been recorded in Ushuaia or the wider archipelago of Tierra del Fuego.

But provincial officials further north in Patagonia where the hantavirus is endemic insist that the first known victims of the outbreak — a Dutch couple passionate about birds — didn't visit during the window in which it is believed they became infected.

The Dutch tourists concluded a sprawling road trip across Chile and Argentina in late March with a few days of bird-watching and trekking in Ushuaia before boarding the ship on April 1.

Health authorities here have fiercely rejected the national government's initial hypothesis that the chain of infections on the cruise began when the couple visited an Ushuaia landfill.

They have both since died, complicating the efforts of Argentine investigators to retrace their path through the country with the aim of determining where they contracted the virus.

Found throughout southern Chile and Argentina, the Andes virus may be able to spread between people in rare cases. Most clusters of the Andes virus, experts say, emerge from exposure to air contaminated with the feces and urine of the long-tailed pygmy rice rat known as the "colilargo" that runs rampant through the forests of northern Patagonia.

The colilargo itself has no presence across the Strait of Magellan in Tierra del Fuego, which is believed to be too cold and isolated, but a subspecies can be found in the forests around Ushuaia, and scientists have never examined whether it can transmit the hantavirus.

Adamant that tourism-dependent Tierra del Fuego isn't the source of the cruise ship outbreak, health authorities here say they welcome a broader objective of the investigation: figuring out if their province has hantavirus at all at a time of global warming.

They said the scientists were trapping rats in two areas where the colilargo subspecies proliferates — the national park and the wooded hillsides overlooking Ushuaia's main pebble beach.

"The province has never done this kind of testing before," Alfaro said. "It's important that we rule out the possibility of transmission occurring here."

The number of hantavirus cases has increased in recent years in Argentina, a trend scientists attribute to colilargos vastly increasing their range as a result of climate change and human encroachment.