The Lombardy outbreak came to light when a 38-year-old Italian tested positive in Codogno, a comune in the province of Lodi. According to his wife, he had met an Italian friend who had returned from China on 21 January, who subsequently tested negative. On 14 February, he felt unwell and went to a doctor in Castiglione d'Adda. He was prescribed treatments for influenza.
On 16 February, as the 38-year-old man's condition worsened, he went to Codogno Hospital, reporting respiratory problems. Initially, there was no suspicion of COVID-19, so no additional precautionary measures were taken, and the virus was able to infect other patients and health workers. Later, the patient, his pregnant wife, and a friend tested positive. Three more cases were confirmed on the same day after the patients reported symptoms of pneumonia. Thereafter, extensive screenings and checks were performed on everyone that had possibly been in contact or near the infected subjects.
The Ministry of Health announced new guidelines for reporting cases on 27 February in response to the previous blanket testing that caused case numbers to surge and inflamed public panic. It would no longer report asymptomatic cases (swabs taken from patients which tested positive but were not showing symptoms) which counted as 40 to 50% of all reported cases at the time. These people would undergo isolation at home and would be followed up with new tests until they were negative.