Brushing your teeth while being treated in hospital can significantly reduce your chances of falling ill with pneumonia.

Many hospitalised patients don’t brush their teeth during their stay, probably for a variety of reasons. Some may have forgotten to bring a toothbrush, while others don’t think about it, feel unmotivated or are physically incapable of doing so. Medical staff often do not include routine oral hygiene care as part of their services to patients.

But in the largest randomised controlled trial of its kind, patients equipped with a toothbrush, toothpaste and dental care advice in hospitals were 60 per cent less likely to develop a common form of hospital-acquired pneumonia, says at Avondale University in Australia.

“This just really enforces the need for communication with patients about pneumonia risk, and the importance of oral care and brushing their teeth whilst in hospital,” he says.

It’s widely understood that patients on often develop pneumonia, due, in part, to the medical equipment interfering with the natural respiratory system. But many non-ventilated hospitalised patients also acquire pneumonia at least 48 hours after hospital admission. Researchers are still trying to understand why this happens and how to prevent it – particularly since hospital-acquired pneumonia is linked to .

“It’s an important problem,” says at Harvard University, who was not involved in the study. “Hospital-acquired pneumonia is one of the most common and deadly healthcare-associated infections, and rigorous data on how best to prevent it are sparse.”

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Mitchell suspected the disease might be linked to the bacteria in people’s mouths. The oral microbiome can affect respiratory health, as people breathe bacteria-laden droplets into their lungs. And the oral microbiome changes when people are hospitalised, says Mitchell. “I felt it was important that we try to do something to address this.”

So, he and his colleagues developed a year-long randomised controlled trial involving 8870 patients in three Australian hospitals to test the effects of oral care on pneumonia risks. He presents the results of this part of the team’s Hospital-Acquired Pneumonia Prevention (“HAPPEN”) study today at the in Munich, Germany.

Each participating hospital divided its study participants into three groups. None of the groups received any intervention for the first three months of the study. After three months, the patients in one group were provided with toothpaste and a toothbrush, labelled “Brushing teeth helps prevent pneumonia” on one side and “Brush away pneumonia!” on the other. The brushes were designed with a special handle for people with reduced dexterity. Patients also received a QR code linking them to educational materials on the .

After six months, the second group also received the toothbrushes, and the third group was given toothbrushes after nine months – meaning all study participants had the option of brushing their teeth for the final three months of the study.

As for the healthcare staff, the research team organised oral care training for ward nurses and provided them with links to professional advice on their website. They also encouraged the nurses to remind patients to brush and floss their teeth and to help those who had difficulty doing so themselves.

Outside of the intervention periods, only 15.9 per cent of the patients brushed their teeth once a day. During the intervention periods, 61.5 per cent of the patients attended to their oral care at least once per day – with patients doing so 1.5 times per day on average. Web statistics revealed that both patients and nurses frequently accessed the information on the HAPPEN pages during the intervention periods, says Mitchell.

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That coincided with a dramatic drop in the number of cases of non-ventilator-associated hospital-acquired pneumonia, says Mitchell. Specifically, the incidence fell from 1 case per 100 admission days in the control group to 0.41 in the intervention group.

“This study is intriguing,” says Klompas, who highlights the large study size and randomised design. “The message is that brushing teeth while in hospital is not only good for one’s oral hygiene and sense of well-being, but it may also literally be life-saving.”

at the University of Helsinki, Finland, says he appreciates the importance of such a significant risk improvement based on such a simple intervention. “Basically the patients were just provided with toothbrushes, toothpaste and advice,” he says. Even so, results might vary depending on reasons for hospitalisation and the patients’ usual oral hygiene habits.

Hundreds of stranded dolphins in Argentina appear to have become trapped while escaping hungry orcas in a tragic lose-lose situation.

Videos shared on social media and citizen science platforms have helped scientists unravel the mystery behind two deadly mass stranding events in recent years, says at the National Scientific and Technical Research Council of Argentina.

“This doesn’t mean predators are always the cause of mass strandings, but it suggests that predator-prey interactions may sometimes trigger these events – particularly when combined with factors such as coastal geography, tides and the strong social behaviour of dolphins,” says Arias.

Marine mammals have been getting stranded in mass mortality events for millions of years, but scientists still debate why they happen. Possible explanations include human disturbance, toxic algae, infectious diseases, disorientation, overpopulation, natural disasters and group hunting efforts that take a wrong turn.

Some research teams have suggested that stranded pods . But that is difficult to document, as hunts cover large spaces and last a long time. “Often researchers only see the final result: a group of dolphins stranded on the beach that appear otherwise healthy,” she says.

In the past five years, common dolphins (Delphinus delphis) have been stranded three times in northern Patagonia – something that hadn’t happened previously – prompting Arias and her colleagues to investigate.

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The researchers analysed video footage from drone cameras and mobile phones uploaded to the citizen science platform and social media sites by tourists, guides, fishers and local residents.

They saw that, in 2021, about 350 dolphins were speeding towards San Antonio Bay in Rio Negro province, Argentina, with a pod of eight orcas (Orcinus orca) about half an hour behind them. At the mouth of the bay, some dolphins headed into the shallow port and lay low and still as if in hiding, while the orcas U-turned back into the sea. The next day, dozens of dolphins were found dead in the port.

Similarly, in 2023, about 570 dolphins raced towards the bay at high speed, followed by a group of orcas. Some of the dolphins rushed into the port, but local authorities and volunteers successfully rescued them after the orcas had turned away.

Necropsies of 38 dead animals from the 2021 event showed they had good body condition and no significant disease or injuries. Their stomachs contained no recent meals – suggesting they weren’t chasing prey. “This makes some of the most common explanations for strandings less likely,” says Arias.

Scientific and lay reports of orca sightings over recent years helped the team establish a chronological map of their presence in the area and revealed two confirmed reports of orcas hunting and killing common dolphins.

The dolphins probably sought refuge in shallow areas that interfere with orcas’ echolocation and movement – but then ended up getting stuck among the sandbanks and tidal channels themselves, says Arias.

Orcas, meanwhile, might deliberately chase dolphins towards bays in an attempt to corner them. In fact, two of the 2021 orcas had been repeatedly sighted using coastal features to trap sea lions, she says.

Prolonged stress and disorientation from the chase might have made the dolphins less likely to find their way back out to sea. Such cases probably occur across the globe and just haven’t been documented yet, says Arias.

“This study highlights the important contribution that citizen science can make to research, and how understanding these processes helps us not only explain mass strandings, but also better understand how marine ecosystems change – and how species respond to those dynamics,” she says.

“This is an interesting and surprising idea,” says at Georgetown University in Washington, DC. “Killer whales do not typically target small delphinids because they are hard to catch, but if they can trap them it might be a more viable strategy.”