In 2000 he entered the National Office for Civil Service. In 2002 he was appointed executive of the Civil Protection Department, the government body in Italy that deals with the prediction, prevention and management of exceptional events. From 2010 to August 2017 he served as Deputy Head of the Civil Protection, and when Fabrizio Curcio resigned, Prime MinisterPaolo Gentiloni appointed him new Head of the Civil Protection. As Head of the Civil Protection he had to face the reconstruction after the August 2016 Central Italy earthquake, which was still to be completed.
On 31 January, the Italian Council of Ministers appointed Borrelli Extraordinary Commissioner for COVID-19 pandemic. In February 2020, Italy became one of the world's main centres for confirmed cases of COVID-19, a virus from China which caused a respiratory disease. In late January, the government banned all flights from and to China, becoming the first European country to adopt this measure. On 22 February, the Council of Ministers announced a bill to contain the COVID-19 outbreak, quarantining more than 50,000 people from 11 different municipalities in Northern Italy. Prime Minister Conte stated: "In the outbreak areas, entry and exit will not be provided. Suspension of work activities and sport events has already been ordered in those areas." Schools were closed in 10 municipalities in Lombardy, one in Veneto and in Emilia-Romagna. In some areas, all public events were cancelled and commercial activities were halted. Regional train services suspended the stops in the most affected areas – with trains not stopping at Codogno, Maleo and Casalpusterlengo stations. Universities in Lombardy suspended all activities from 23 February. On 8 March 2020, on the advise of the Civil Protection scientific committee, Prime Minister Conte extended the quarantine to all of Lombardy and 14 other northern provinces, putting more than a quarter of the national population under lockdown. On the following day, he announced in a press conference that all measures previously applied only in the so-called "red zones" had been extended to the whole country, putting de facto 60 million people in lockdown. He later proceeded to officially sign the executive decree. This measure was described as the largest lockdown in human history. On 20 March, the Ministry of Health ordered tighter regulations on free movement. The new measures banned open-air sports and running, except individually and in close proximity of one's residence. Parks, playgrounds and public green were closed down. Furthermore, movement across the country was further restricted, by banning "any movement towards a residence different from the main one", including holiday homes, during weekends and holidays. While on the following day, Conte announced further restrictions within the nationwide lockdown, by halting all non-essential production, industries and businesses in Italy, following the rise in the number of new cases and deaths in the previous days. On 24 March, a new decree imposed higher fines for the violation of the restrictive measures, and a regulation of the relationship between government and Parliament during the emergency. It included also the possibility of reducing or suspending public and private transport, and gave the regional governments power to impose additional restrictive regulations in their Regions for a maximum of seven days before being confirmed by national decree. On 1 April, the period of lockdown was extended until 13 April. While on 6 April, Conte announced a new economic stimulus plan, consisting of €200 billion of state-guaranteed loans to companies and additional €200 billion of guarantees to support exports. On 10 April, Conte made further announcements extending the lockdown until the 3rd of May, allowing some specific businesses, like bookstores and silviculture activities, to reopen under specific safe measures. On the same day, he appointed a task force to relaunch Italy after the crisis; the team was led by Vittorio Colao and composed by a total of nineteen members, chosen among university professors, managers and public administration officers, which notably included Mariana Mazzucato and Enrico Giovannini.
