Andes Hantavirus Explained: Why the MV Hondius Strain Is Different From Most

Most people have never heard of hantavirus. Fewer still know that one specific strain of it, the Andes virus, now at the centre of the MV Hondius outbreak, is the only type in the world known to spread directly between humans. That single fact is why scientists and health officials are watching this situation so carefully.

The MV Hondius outbreak has been linked to the Andes strain of hantavirus, a rare but potentially severe virus that, in some cases, can spread between humans through close contact, unlike virtually every other hantavirus strain known to science, which only spreads from infected rodents to people. 

The Andes virus is endemic to southern South America, particularly Argentina and Chile. WHO is working on the assumption that the Dutch couple who died were infected before boarding, possibly during a birdwatching trip that took them through Argentina, Chile, and Uruguay, areas where the species of rat known to carry the virus is present. Argentine investigators are now tracing the couple's exact movements across a four-month road trip that began in November 2025.

Once infected, the disease typically begins with fever and gastrointestinal symptoms before rapidly progressing to pneumonia and acute respiratory distress syndrome. In severe cases, it can lead to circulatory shock. Illness onset among MV Hondius patients occurred between April 6 and April 28.

There is no approved antiviral treatment for hantavirus. Critically ill patients require intensive care, including mechanical ventilation in cases of severe respiratory failure. The case fatality rate for Hantavirus Pulmonary Syndrome, the form caused by the Andes strain, has historically been high, ranging from 35 to 50 per cent in documented outbreaks.

Health officials have dismissed comparisons to COVID-19, stressing that hantavirus does not spread through the air like respiratory viruses do and that the risk of a large-scale epidemic is extremely low. Human-to-human transmission of the Andes strain has been documented only in cases involving prolonged, intimate contact, not casual interaction aboard a ship.

Argentina's health ministry reported 101 hantavirus infections in the country since June 2025, roughly double the caseload recorded over the same period the previous year, suggesting that, even before this outbreak, the virus was circulating more actively than usual in South America.