US Vice-President Mike Pence plans to maintain a busy election campaign schedule despite being exposed to a senior aide who has tested positive for Covid-19, his spokesman says.

US President Donald Trump’s running mate will not self-isolate, although he is a close contact of the VP chief of staff, Marc Short.

Pence and his wife both tested negative on Sunday, his office said. Covid-19 has become a key battleground ahead of the November 3 election, the BBC reported.

About 57 million ballots have already been cast in early voting, a record figure largely spurred by the pandemic.

Trump’s Democratic challenger, former Vice-President Joe Biden, holds an average eight-point lead in national polls. But the race is much closer in several important swing states.

Pence – who leads the White House Coronavirus Task Force – and his wife, Karen, remained “in good health”, his spokesman Devin O’Malley said in a statement.

“While Vice-President Pence is considered a close contact with Short, in consultation with the White House Medical Unit, the vice-president will maintain his schedule in accordance with the CDC (Centers for Disease Control and Prevention) guidelines for essential personnel,” he added.

Those measures include regular monitoring for symptoms and mask-wearing. CDC guidelines also state that those who have had close contact with someone who has Covid-19 should self-isolate for 14 days.

Speaking on CNN, White House chief of staff Mark Meadows said Pence continued to perform “essential” duties as vice-president, but did not explain how his campaign activities could be classified as “essential”.