Pandemic curbs behind early start to Europe’s flu season

Scientists say Covid restrictions may have created a bigger pool of susceptible people

Pandemic restrictions that hampered the circulation of viruses other than Covid-19 could be behind the unseasonably early upsurge in respiratory infections in Europe this winter that the festive break could prolong, scientists say.

Regulations to curb movement and social interaction limited the transmission of viruses that typically cause most infections during winter, including influenza and RSV (respiratory syncytial virus).

That created a bigger pool of susceptible people, including children born during this time, who had less exposure.

RSV usually causes mild, cold-like symptoms, but can result in serious illness in older adults and young infants.

Tripledemic warning

This winter, health officials have warned of what has been dubbed a tripledemic of influenza, RSV and continued Covid-19 cases, adding to the pressure on health services.

European trends so far suggest that this year RSV cases peaked in late November and are in decline, but there will still be a substantial number of cases in the next four to six weeks, said Agoritsa Baka, the the European Centre for Disease Prevention and Control’s (ECDC) expert in emergency preparedness and response.

Meanwhile, Covid cases have risen in recent weeks. In the week ended December 18, European cases rose 7 per cent over the week prior, according to ECDC figures.

The flu upsurge began in the second week of November in the European region, an earlier start than the four previous seasons, the agency said. “The accumulation of more susceptible persons in the last two years, plus the increased mixing of people during the summer months [following the easing of restrictions] have contributed to an earlier start of the outbreaks in the current season 2022-2023,” Baka said.

With little in the way of direct comparison with the situation this year, it is unclear whether sharp peaks earlier than usual will necessarily lead to a higher number of cases over the season.