A 90-year-old woman who died after falling ill with Covid-19 was infected with both the Alpha and Beta variants of the coronavirus at the same time, researchers in Belgium said, adding that the rare phenomenon may be underestimated.

The unvaccinated woman, who lived alone and received at-home nursing care, was admitted to the OLV Hospital in the Belgian city of Aalst after a spate of falls in March and tested positive for Covid-19 the same day.

While her oxygen levels were initially good, her condition deteriorated rapidly and she died five days later, AFP reported.

“Both these variants were circulating in Belgium at the time, so it is likely that the lady was co-infected with different viruses from two different people,” said molecular biologist Anne Vankeerberghen from the OLV Hospital who led the research.