Scientists have issued a stark warning that the recent outbreak of hantavirus on a cruise ship could be just the beginning, as climate change is expected to drive a surge in rodent-borne viruses.
In a new study, researchers reveal that rising global temperatures and shifting rodent populations will lead to enhanced 'spillover' of deadly arenaviruses into areas that have never faced these diseases before. The findings suggest that outbreaks could threaten millions of people across South America.
The warning comes as more than 20 British nationals remain trapped aboard a cruise ship infected with rat-borne hantavirus off the coast of Cape Verde. Three passengers have died, including a Dutch couple and a German national. The Dutch-flagged MV Hondius had previously docked in Argentina, where both hantavirus and arenaviruses claim dozens of lives each year.
Like hantavirus, arenaviruses are hosted by rodents and typically spread to humans from animals rather than through person-to-person infection. These extremely common but poorly studied infections include Guanarito virus in Venezuela and Colombia, Machupo virus in Bolivia and Paraguay, and Junin virus in Argentina. Infection causes severe hemorrhagic fevers with high hospitalisation rates, and fatality rates range from five to 30 per cent.
Since these diseases are spread by rodents, their impact is closely linked to changes in rodent habitats. Previous research has shown that factors such as temperature and precipitation have a massive impact on the risk of rodent-borne diseases like Lassa fever and hantavirus. The distribution of the drylands vesper mouse, which transmits Argentine Hemorrhagic Fever, will undergo 'substantial changes' due to climate change.
In their paper, the researchers used machine learning to combine climate projections, population density predictions, infection risks, and habitat suitability for six rat and mouse species linked to the viruses. This revealed that the infection risk posed by these dangerous diseases would change dramatically in the next 20 to 40 years under different climate change scenarios.
Lead author Dr Pranav Kulkarni, of the UC Davis Weill School of Veterinary Medicine, said: 'As climate change accelerates, our study shows how the outbreak risk of dangerous New World arenaviruses could ride on shifting rodent populations to reach millions more people across South America.'
The model shows that the Guanarito virus, currently contained to central Venezuela, will spread to parts of Colombia, the border regions of Suriname, and northern Brazil. The Machupo virus, which causes often fatal Bolivian Hemorrhagic Fever, will expand from the flatlands of Bolivia to the Andes foothills and mountain regions. Meanwhile, the Junin virus that causes Argentine Hemorrhagic Fever will move out of grassland areas and expand across the rest of Argentina.
This will reduce the risk in some areas that have already learned to deal with the disease, but increase the dangers of infection in others. In all cases, Dr Kulkarni and his co-authors warn that populations with little or no prior exposure will be encountering these viruses for the first time, potentially increasing their vulnerability to infection and severe disease.
Senior author Dr Pranav Pandit added: 'Our study connects the dots between changing climatic conditions and land use, shifting rodent populations and human infection risk, making it possible to see where the next generation of zoonotic arenaviral outbreaks could emerge.'
These changes were primarily driven by expanding agricultural and urban areas, bringing more humans into the habitats of rodents capable of carrying arenaviruses. Combined with climate-driven changes in the rodents' habitats, triggered by temperature and precipitation shifts, major outbreaks in previously safe areas are likely.
The research comes after an outbreak of rodent-borne hantavirus left a luxury cruise ship stranded at sea. The MV Hondius vessel has been anchored in the Atlantic since Sunday, following the death of three passengers. Around 150 people remain aboard, while the World Health Organisation has confirmed six cases of hantavirus. It is suspected that the virus may have been transmitted during a stop in South America, either directly to humans or to rodents aboard the ship.
A spokesperson for the Netherlands' National Institute for Public Health and the Environment told Reuters: 'You could imagine, for example, that rats on board the ship transmitted the virus. But another possibility is that during a stop somewhere in South America, people were infected, for instance via mice, and became ill that way.'
