Morbillivirus detected in whales beyond the Arctic Circle

Already weakened by human activity and climate disruption, the giants of the sea living beyond the Arctic Circle are now confronting another threat. These isolated whale populations, exposed to this virus, are worrying scientists, who fear that these environmental pressures could trigger a devastating die-off.

Monitoring the health of the largest members of marine megafauna has always posed a major challenge for biologists and oceanographers. How can they examine animals weighing several dozen tonnes, spending 90% of their time underwater and travelling thousands of kilometres each year? Cetaceans are not particularly afraid of people, but getting close to them requires highly complex interventions: any handling or sedation is exceptionally dangerous because, unlike land mammals, these animals breathe only through a strictly voluntary action.

To avoid such hazardous procedures, researchers now favour non-invasive approaches, including drones that collect health data remotely. By analysing the exhaled breath of whales beyond the Arctic Circle, a team of scientists made an alarming finding: several animals were infected with a pathogen feared in marine environments, morbillivirus. Their study of this contamination was published on 18 December in BMC Veterinary Research: a previously unrecorded observation at these latitudes.

Drones: the oceans’ new stethoscope

The sampling was carried out using ordinary commercial drones. Researchers flew them over the whales as they surfaced to breathe. Fitted with sterile collection plates, the devices could be placed within the plume of vapour expelled through the animal’s blowhole. This “cloud” is actually condensed water vapour; it is expelled at remarkable speed, between 400 and 700 km/h, and enables whales to clear mucus.

This valuable biological deposit contains cells, microbes and viral genetic material originating directly from the cetacean’s respiratory system. “Drone sampling is a game changer,” says Terry Dawson, co-author of the study. “It allows us to monitor pathogens in living whales without causing them any stress, providing critical information on rapidly changing Arctic ecosystems.”

From 2016 to 2025, the technique enabled the team to assess the health of numerous individuals across the North Atlantic, from Iceland to the coast of northern Norway. They examined humpback whales (Megaptera novaeangliae), sperm whales (Physeter macrocephalus) and fin whales (Balaenoptera physalus).

Morbillivirus: an unexpected threat in Arctic whales

Once the samples had been examined in the laboratory using methods similar to those used in human disease surveillance, the findings were clear. Scientists identified genetic markers of cetacean morbillivirus (CeMV), a highly aggressive, so-called multisystemic virus that causes pneumonia and brain diseases, particularly encephalitis, and can even completely destroy the immune system of infected cetaceans.

It is one of the most destructive pathogens affecting marine mammal populations worldwide. Spread through the respiratory route, it has previously caused major mortality events among dolphins and whales.

The discovery is especially troubling because it confirms for the first time that the virus is circulating among these cetacean populations - with some animals showing signs of weakness - at latitudes where it had never previously been detected.

As ocean waters warm and sea ice declines, whales tend to gather in denser groups than before during winter feeding seasons. For Helena Costa, the study’s lead author, this is likely to be one explanation for the circulation of CeMV. “These gatherings, combined with environmental stress and greater proximity to other species or human activities, create fertile ground for disease transmission,” she notes.

“The priority now is to sustain this monitoring over time, so that we can better understand how the growing number of environmental pressures affects whale health,” the researcher continues. Without this long-term surveillance, it will be very difficult to establish whether this is simply a temporary epidemic peak or a genuine increase in the prevalence of this virus among these cetaceans. The animals studied are already closely monitored by conservation bodies, with some - including sperm whales and fin whales - considered highly vulnerable. Should an inadequately anticipated outbreak occur, losses could quickly reach hundreds of individuals: a grim illustration of our glaring inability to foresee the consequences of our own actions.