Several of the most fiercely contested states in the US presidential election showed sharp increases in coronavirus cases on Thursday, pushing the number of infections nationwide to their highest levels since a summer outbreak.

Wisconsin, Ohio and North Carolina — which Donald Trump won four years ago but where statewide polling shows Democratic challenger Joe Biden either even or leading — recorded record jumps in cases, according to local health departments.

In addition, Arizona and Florida, which are also viewed as “swing states” that Mr Biden could win after they went for Mr Trump in 2016, had big jumps in infections on Thursday. Arizona reported more than 1,000 new infections for the first time in a month, while Florida recorded 3,573 new cases, its second-highest total in the past month.