The US and several European countries have reported their highest daily rises in Covid cases since the pandemic began, as the Omicron variant spreads.
More than 440,000 new cases were recorded in the US on Monday, health officials said.
France, Italy, Greece, Portugal and England have also reported record numbers of daily infections.
Officials have said the high figures could be due in part to reporting delays over the Christmas period.
Poland on Wednesday recorded 794 Covid-related deaths, the highest number in its fourth wave of the pandemic, with more than three-quarters of the victims unvaccinated.
In the US, cases recorded by the US Centers for Disease Control and Prevention (CDC) rose by 441,278 on 27 December – by far the highest number of daily cases ever reported to the agency.
The CDC data tracker says US media report the seven-day average rise in infections is now at its highest level since January 2021.
A CDC spokeswoman told news site Politico that the latest infection figures could be overestimated due to lags in testing and test centre closures over the Christmas period, adding that case numbers would “become more stable after the new year”.
The health agency has also expanded its travel warnings for parts of Europe, adding Malta, Moldova and Sweden to a list of countries where travel poses a very high risk of infection.
Travellers are asked to avoid these countries under the CDC’s Level 4 criteria, which a destination receives if it reports more than 500 cases per 100,000 people.