According to the study, between 2016 and 2018, 338 swine production workers in China were tested for antibodies of the virus, and 35 (10.4%) had tested positive. Of those workers between the ages of 18 and 35, 20.5% had tested positive. Among another 230 people screened who did not work in the swine industry, 10 (4.4%) tested positive for antibodies, indicating prior infection. Three cases of infection caused by the G4 virus had been documented as of July 2020, with no confirmed cases of human-to-human transmission.