LISBON, Portugal (AP) — Portugal's Socialist Party leader António Costa announced Tuesday he has tested positive for COVID-19, two days after his landslide election victory and just as he starts forming his new government.

Costa said in a statement he will self-isolate for seven days, in accordance with the country's pandemic rules.

Costa, who has been Portugal's prime minister since 2015 and is set to serve another four years, was due to meet with President Marcelo Rebelo de Sousa on Wednesday as a first step toward being sworn in. It wasn't immediately clear if another Socialist Party official would replace him.

The Socialists took at least 117 seats in Portugal's 230-seat parliament, with four seats still to be allocated, in what was a thumping victory.

Costa, along with scores of Socialist officials and supporters, celebrated the rout in a windowless basement room in a Lisbon hotel, with hugging and yelling.

Media representatives were also present for Costa's victory speech in the packed and low-ceilinged room, which drew criticism as a poor choice of venue for celebrations.

People were required to show digital vaccine certificates and wear masks at the event, but checks were not always carried out and some people pulled their masks down to their chin.

The election took place amid a surge in COVID-19 cases blamed on the omicron variant. Around 1 million people were in home confinement on election days but they were allowed to go out to vote.

Follow AP’s pandemic coverage at https://apnews.com/hub/coronavirus-pandemic