An excruciatingly painful tropical disease called chikungunya can now be transmitted by mosquitoes across most of Europe, a study has found.

Higher temperatures due to the climate crisis mean infections are now possible for more than six months of the year in Spain, Greece and other southern European countries, and for two months a year in south-east England. Continuing global heating means it is only a matter of time before the disease expands further northwards, the scientists said.

The analysis is the first to fully assess the effect of temperature on the incubation time of the virus in the Asian tiger mosquito, which has invaded Europe in recent decades. The study found the minimum temperature at which infections could occur is 2.5C lower than previous, less robust, estimates, representing a “quite shocking” difference, the researchers said.

Chikungunya virus was first detected in 1952 in Tanzania and was confined to tropical regions, where there are millions of infections a year. The disease causes severe and prolonged joint pain, which is extremely debilitating and can be fatal in young children and older adults.

A small number of cases have been reported in more than 10 European countries in recent years, but large-scale outbreaks of hundreds of cases hit France and Italy in 2025.

Sandeep Tegar, at the UK Centre for Ecology and Hydrology (UKCEH) and lead author of the study, said: “The rate of global warming in Europe is approximately double the rate of global warming at global scale and the lower temperature limit for virus spread matters a lot, so our new estimates are quite shocking. The northward expansion of the disease is just a matter of time.”

Dr Steven White, also at UKCEH, said: “Twenty years ago, if you said we were going to have chikungunya and dengue in Europe, everybody would have said you were mad: these are tropical diseases. Now everything’s changed. This is down to this invasive mosquito and climate change – it really is as simple as that.

“We’re seeing rapid change and that’s the worry. Up until last year, France had recorded 30-odd cases of chikungunya over the last 10 years or so. Last year, they had over 800.” The virus was carried by travellers from French overseas territories in the tropics where there were outbreaks, including Réunion.

The Asian tiger mosquito (Aedes albopictus), which bites during the day, is moving northwards across Europe as temperatures rise. It has been detected in the UK but is not yet established. There are costly vaccines for chikungunya but the best protection is to avoid being bitten.

Dr Diana Rojas Alvarez, who leads the World Health Organization’s team on viruses transmitted by insect and tick bites, said: “This study is important because it indicates that transmission [in Europe] might become even more evident over time.” She added that chikungunya can be devastating, with up to 40% of people still experiencing arthritis or very severe pain after five years.

“Climate has a huge impact on this, but Europe still has the chance to control these mosquitoes from spreading any further,” she said. Community education on removing the still water where mosquitoes breed is one important tool, while wearing long, light-coloured clothing and using repellent prevents bites. Health authorities also need to set up surveillance systems, she said.

When a mosquito bites an infected person, the chikungunya virus enters its gut. Then, after an incubation period, the virus is present in the mosquito’s saliva, meaning it can infect the next person it bites. But if that incubation period is longer than the lifespan of the mosquito, the virus cannot spread.

The study, published in the Journal of Royal Society Interface, used data from 49 earlier studies on chikungunya virus in tiger mosquitoes to determine the incubation time across the full range of temperatures for the first time.

The study found the cut-off temperature for transmission is 13C-14C, meaning infections can occur for more than six months of the year in Spain, Portugal, Italy and Greece, and for three to five months of the year in Belgium, France, Germany, Switzerland and a dozen other European countries. The minimum temperature was previously estimated at 16C-18C, meaning there is a risk of chikungunya outbreaks in more areas and for longer periods than previously thought.

The new work gives much more detailed information on the areas at risk. “Identifying specific locations and the months of possible transmission will enable local authorities to decide when and where to take action,” Tegar said.

Outbreaks in Europe are sparked by infected travellers returning from tropical regions and being bitten by local tiger mosquitoes, which then spread the disease. Until now, Europe’s cold winters have stopped tiger mosquito activity and acted as a firebreak for the disease from one year to the next.

However, scientists are starting to see all-year-round tiger mosquito activity in southern Europe, meaning chikungunya outbreaks are likely to amplify as the continent warms. The UKCEH team is investigating this issue. “Our intuition is that we’re going to get much bigger outbreaks because you don’t have this natural firebreak,” White said.

There have not yet been any local transmissions of chikungunya reported in the UK, but there were a record 73 cases among people who contracted the virus abroad between January and June 2025, almost three times higher than in the same period in 2024.

White said: “It is important there is continued action to try to prevent the tiger mosquito from establishing in [the UK] because this highly invasive species is capable of transmitting several infections that can cause serious health conditions including chikungunya, dengue and Zika viruses.”

When the COVID-19 pandemic hit in 2020, schools around the globe had to switch from regular, in-person classes to online learning overnight. This introduced numerous operational challenges, particularly in equipping students with quantitative skills essential for the labor market.

New research from the University of Notre Dame looks at how the abrupt move from classroom teaching to online learning during the lockdown affected college students’ performance in China.

Surprisingly, the undergraduates performed better in math after switching to online classes — improving their scores by about eight to 11 points on a 100-point scale, according to Shijie Lu, the Howard J. and Geraldine F. Korth Associate Professor of Marketing at Notre Dame’s Mendoza College of Business. Lu’s research, “Effectiveness of Online Education During the COVID-19 Pandemic: Evidence from Chinese Universities,” is forthcoming in Production and Operations Management.

Along with Xintong Han from Laval University in Quebec City, Shane Wang from Virginia Tech and Nan Cui at Wuhan University in China, Lu analyzed more than 15,000 course records from nearly 8,000 students across nine universities. They compared students’ grades from before the pandemic, when they learned in person, to those during the lockdown when all classes moved online.

Results varied depending on the subject and the lockdown environment. Online learning worked especially well for reasoning-based subjects such as mathematics, where students could pause lectures, rewatch examples and practice problems at their own pace. In contrast, courses such as English that rely on discussion and interpretation, and are challenging to replicate effectively in virtual environments, benefited much less from the online format.

“Contrary to the widespread belief that online education is less effective than face-to-face instruction, our findings show that students actually performed better online, at least in quantitative subjects during the pandemic,” said Lu, who specializes in business analytics and digital marketing. “This challenges the traditional view that in-person learning is always superior and suggests that, under certain conditions, well-structured online environments can enhance learning outcomes.”

Results were linked to the strictness of stay-at-home orders or transportation bans to see how different types of governmental lockdown policies shaped learning outcomes. Using rigorous econometric methods, the researchers made sure that the improvements they observed were due to the switch to online learning and not other unrelated factors.

They found that stricter stay-at-home orders issued by the government raised psychological stress and reduced the effectiveness of online learning. However, these negative effects were partially offset when workplace closures and public transportation suspensions helped some people maintain focus and discipline.

One possible explanation is that as parents were more frequently home due to employment interruptions, they were better positioned to ensure their children attended virtual classes, remained focused on tasks and followed a structured schedule. Meanwhile, suspension of public transportation reduced opportunities for social outings and non-academic distractions, effectively creating a quieter, more focused study environment at home.

“Our results show that online education when done thoughtfully can be more than just a backup plan during emergencies,” Lu said. “It can be an effective tool for learning, especially in analytical subjects.”

For educators, this means designing online courses that take advantage of digital tools — such as interactive exercises or on-demand videos — rather than simply moving lectures onto Zoom. For policymakers, it highlights that not all lockdown policies have the same effect on educational outcomes. Strict stay-at-home orders hurt learning, but moderate workplace closures that allow parents to supervise their children help to improve outcomes.

“These insights can help schools and governments better prepare for future disruptions — whether from pandemics, natural disasters or other emergencies — by understanding how to balance safety and learning effectiveness,” Lu said.

The study shows that online learning programs need to be flexible and designed with the specific course material and students’ physical location in mind.

Contact: Shijie Lu, 574-631-5883, slyu@nd.edu