Question: Do we know any more about characteristics and health outcomes of people who remain asymptomatic? Do we know why some people remain asymptomatic?

Answer: Mostly, these questions are still outstanding, and scientists are trying to answer them. When it comes to your first question, there was an interesting piece of research published on this topic yesterday in JAMA, “Comparison of Clinical Characteristics of Patients with Asymptomatic vs Symptomatic Coronavirus Disease 2019 in Wuhan, China.” I’ll give you a snapshot of its findings.

In short, 78 individuals from 26 cluster cases were enrolled in the study based on the following criteria: 1) they had been exposed to SARS-CoV-2 at the Hunan seafood market or had close contact with a patient who had been hospitalized with confirmed COVID-19; 2) they were confirmed to have SARS-CoV-2 infection. Those 78 individuals were all hospitalized in same place, and provided the same care by the same health workers. 33 patients (42%) were asymptomatic, while 45 patients (58%) were symptomatic. Symptoms were monitored daily and patients were tested for the virus every 24–48 hours. Patients also received chest scans. I’ve copied the article’s Table below, which presents findings. What you see is that compared with symptomatic patients, asymptomatic patients were statistically significantly (p<0.05) more likely to be young and female; less likely to have pre-existing liver injury; more likely to have quicker recovery times and a shorter viral shedding period; less likely to have fluctuating test results; and less likely to have damage done to their immune systems.

Table. Differences between Symptomatic and Asymptomatic Patients