Table 1.

Infection type and social relations of confirmed COVID-19 cases in Shandong province.

Infection type	Social relations	Number
Staying in other regions	Long-term or short-term residence	274
Major events	Ren Cheng prison	207
Family gathering	Father–son relationship, mother–son relationship, married couples relationship, mother-in-law relationship, mother–daughter relationship, other kinship	148
Work and study outside the province	Work, study	55
Visiting family members	Inter-provincial, province-wide	32
Travel	International travel, domestic travel	28
Overseas contact	From Italy	1
Public places	Market, supermarket, hospital	26

Close contact refers to infection without clear social relationship.