The hantavirus outbreak detected on the cruise ship MV Hondius has opened new questions about the person-to-person transmission capacity of the Andes variant, one of the few strains associated with human infections in specific circumstances. However, the World Health Organization (WHO) maintains that the risk to the general population remains low and dismisses treating the situation as an epidemic alert.
According to El Mundo, experts investigating the outbreak are studying whether continuous cohabitation and the enclosed spaces on the ship could have favored a chain of contagion among passengers. The newspaper includes statements from specialists who point out that the cruise ship environment—with shared dining rooms, constant proximity, and enclosed common areas—could have facilitated the horizontal transmission of the virus.
Even so, both the WHO and the Spanish Ministry of Health insist that hantavirus does not present a transmission pattern comparable to that of respiratory viruses such as influenza or covid-19. Transmission between people is still considered infrequent and normally associated with close and prolonged contact.
The Minister of Health herself, Mónica García, recalled this week that human transmission "is not common" and that documented cases have occurred in situations of "close and direct contact" with symptomatic people.
What the WHO is investigating about the cruise ship
The WHO confirmed that the outbreak affects the Andes variant of hantavirus, detected mainly in South America. The main hypothesis the organization is considering is that the first affected individuals were infected before boarding, after a trip through South America, and that secondary transmission could have subsequently occurred on the ship.
During a public appearance, the Director-General of the WHO, Tedros Adhanom Ghebreyesus, recalled that in previous outbreaks of Andes hantavirus "person-to-person transmission has been associated with close and prolonged contact," especially between household members, partners, or healthcare personnel.
Maria Van Kerkhove, technical lead for epidemics at the WHO, also insisted that the organization does not consider there to be a risk of widespread expansion. “We are talking about an outbreak on a ship, in a confined area,” she noted. According to the WHO, the global risk to the population remains low.
Experts talk about coexistence and shared spaces
One of the points that researchers are analyzing the most is the role of enclosed spaces and prolonged coexistence. El Mundo collects statements from Daniel Antenucci, an associate researcher at the Argentine Conicet and a specialist in hantavirus, who relates the possible transmission to continuous proximity within the boat.
According to what the expert explained to the newspaper, sharing enclosed environments for long periods can increase the probabilities of contagion between people in the case of the Andes variant.
However, even specialists who study these cases emphasize that the transmissibility of hantavirus is very different from that of other respiratory viruses. The US CDC recalls that most infections continue to occur through contact with infected rodents or with particles contaminated by saliva, urine, or excrement.
The US agency also maintains that transmission between people is extremely infrequent and that it has only been clearly documented in certain South American variants.
The Argentine precedent that investigators are following
Part of the current investigations are looking towards the outbreak registered between 2018 and 2019 in Argentine Patagonia, one of the most studied episodes of human transmission of the Andes hantavirus.
That outbreak affected dozens of people and led researchers to analyze the possible role of so-called "super-spreaders," patients with high viral loads who could transmit the virus in social gatherings or shared spaces.
The scientific studies published later concluded, however, that even in those scenarios transmission remained limited and much lower than that observed in highly contagious respiratory diseases.
While investigations into the MV Hondius continue, international health organizations maintain the same message: hantavirus is not a new virus, human-to-human transmission remains rare, and the risk of a widespread outbreak continues to be considered low.