The front-runner in Peru"s presidential race, left-winger Pedro Castillo, returned to the campaign trail on Friday, a day after he was rushed to a clinic in the capital Lima for treatment for a respiratory illness, he told supporters in a tweet. Castillo said doctors diagnosed a throat infection and that he would return to active campaigning as well as participating in his first debate on Saturday with rival in the June run-off, Keiko Fujimori. "Nothing will stop us in our march with the people towards a shared dream of justice and freedom," he wrote. Castillo, a 51-year-old primary school teacher, fell ill shortly after arriving to hold rallies in Lima on Thursday following several days of campaigning in northern Peru. The leftist candidate had stretched his lead to 20 points ahead of right-wing Fujimori five days ago but the latest poll suggests that has now narrowed with just over a month to go until the election in the world"s second-largest copper producer. Datum International said on Friday that Fujimori, the daughter of the jailed ex-president Alberto Fujimori, bolstered her support by eight percentage points to 34%, while Castillo"s approval grew only three percentage points to 44%. The poll, published in financial daily Gestion, showed the number of undecided voters shrank to 22% from 33% previously. Fujimori"s support grew most notably in Lima, home to nearly a third of the country"s population, rising to 50% from 34%, while Castillo"s support firmed to 65% from 54% in southern mining regions, the survey said. Castillo, who has pledged to draft a new constitution to give the state more control over the economy, also remains on top in the country"s poorer areas while Fujimori, who has promised to shield Peru"s free-market model, polls stronger in wealthier areas. Bond prices ticked higher on Friday even as Castillo returned to the campaign trail, according to Refinitiv data, following sharp drops earlier in the week. The new study was carried out between April 27 and 29 on 1,200 people and has a margin of error of +/- 2.8%.