Even asymptomatic people who are infected may be able to spread the virus. But people without symptoms are rarely tested. In Anyang, China, five members of a family came down with the coronavirus after hosting a guest from Wuhan in early January.
https://www.nytimes.com/2020/02/26/health/coronavirus-asymptomatic.html
https://www.nytimes.com/2020/02/26/health/coronavirus-asymptomatic.html