Eighty-six percent of people in China who were infected with novel coronavirus (SARS-CoV-2) were not tested in the two week period before travel restrictions came into force on January 23 in Wuhan and other cities. And these undetected cases contributed to the majority of virus spread in the community, says a paper published in the journal Science. The paper says that undetected cases can expose a large population to the virus than would otherwise occur. The study found undetected cases were the source of infection for 79% of documented cases.
via Coronavirus: Undetected cases drive virus spread in the community — Science Chronicle
And this is precisely why you must stay at home as much as possible in the near term future. Limit your movements, avoid crowds, use common sense.
lifeunderwriter.net 
From your readings of professional journals, can an individual be infected twice by the COVID19
coronavirus? A Facebook friend, posted anecdotal evidence of four or five people testing positive, getting sick, testing negative, and then testing positive again.
From my journal scanning I’ve found nothing from a medical/scientific basis to support the reinfection hypothesis. I have read anecdotal stories from China written by journalists stating the reinfection theme. There’s also a story about patients being turned away from hospitals and/or being discharged without receiving any medical attention. As none of this can be verified, I don’t repeat the stories.
Thank you very much. This is why I appreciate your blog posting so much.