Although the current hantavirus outbreak has infected 11 people and claimed the lives of three, experts emphasized that the risk for the general public remains low.
In early April, the MV Hondius cruise ship sailed off the Argentinian Tierra del Fuego region destined for Cape Verde on the coast of West Africa. During the month that ensued, passengers began to exhibit signs of severe respiratory illness, which claimed the lives of three of the nearly 150 people onboard.
In May, the World Health Organization (WHO) confirmed a hantavirus outbreak on the cruise ship. As of May 12, 11 cases of the disease have been reported, with nine confirmed as hantavirus infections by testing; the other two are suspected cases.
Even though hantavirus infections can be deadly, reported cases are rare. In the US, 890 cases of hantavirus disease were reported from 1993 to 2023, according to the Centers for Disease Control and Prevention. Despite the low number of cases in humans, the recent events on the cruise ship have fueled concerns among people in the US and elsewhere.
“It’s totally understandable that, given the recent events with COVID, people are now more afraid, especially if it’s a virus causing lung disease,” said Manuel Schibler, a physician and head of the virology laboratory at the Geneva University Hospital. “This virus is much less fit to be transmitted from one human being to another than was, or still is, SARS-CoV-2.”
Hantaviruses are a group of closely related viruses that can be found across the world. These single-stranded RNA viruses can be classified into two major groups: Old and New World hantaviruses. The Old World viruses are found in Europe and Asia and can cause hemorrhagic fever with renal syndrome (HFRS). The New World hantaviruses are distributed across the Americas and cause hantavirus cardiopulmonary syndrome (HCPS), as was reported on the cruise ship.1 In the late 1970s, researchers identified the first hantavirus, known as Hantaan virus, and recognized it as the causative agent of HFRS—a disease that caused an outbreak nearly 25 years earlier during the Korean War.2
Rodents of different species are the primary reservoirs of hantaviruses, but some species of shrews, moles, and bats can also harbor these viruses. Human infections result from exposure to aerosols of rodent excreta (urine or feces) containing viral particles.1
Schibler, who oversees the Swiss reference center for emerging viral infections, obtained a sample from an infected Swiss national cruise passenger for diagnosis. Using a polymerase chain reaction (PCR) test specifically designed to identify different hantavirus species, his team found that the virus infecting the patient and causing the cruise ship outbreak belonged to the Andes species, a New World type of hantavirus most commonly associated with infections in South America.1 Schibler explained that the Andes species had been suspected to be behind the outbreak, as the evidence suggested that the first exposure may have occurred in Argentina, and there was indication of potential human-to-human transmission—a feature known to happen only with the Andes hantavirus species.3
“For all the outbreaks of the Andes virus so far, where there’s been person-to-person transmission, the key factor seems to be that the people who were infected had prolonged close contact,” explained Andrew Fleming, an infectious disease specialist at the New York University Langone Hospital Brooklyn. “That tells us that it’s actually not very easy to transmit this virus.” Fleming added that, unlike SARS-CoV-2, the Andes virus is not spread by people who do not show symptoms. Those infected with Andes virus show clear symptoms of the disease, which makes identifying and managing potentially infected people easier.
Both Schibler and Fleming noted that, even though person-to-person transmission of the Andes virus does occur, it is very rare, keeping the risk to the general public low.
As for the current outbreak on the cruise ship, Fleming emphasized that tracking potentially infected passengers and monitoring them for symptoms are essential steps now. “As long as we can do that,” he said, “then there’s not really a major risk of the virus being transmitted to anybody else.”