In total, the study team at ISTH analysed more than 4,800 samples. In the first month after discharge, they found low levels of Lassa virus RNA in 26 percent of plasma, 19 percent of urine, 3 percent of saliva, 4 percent of lacrimal fluid, and 9 percent of vaginal swab samples. All samples of these body fluids became negative three months after discharge at the latest.
In contrast, more than 70 percent of the collected seminal fluid samples were found to contain consistently high concentrations of Lassa virus RNA within the first month. Six months after discharge, almost 20 percent of the samples were still positive, and 2 percent remained positive for up to twelve months after recovery. A total of three quarters of all study participants, who provided at least one seminal fluid sample, were at least positive at one timepoint - a clear majority. Using a mathematical model of the data, the researchers calculated that 50 percent and 10 percent of male survivors still shed Lassa virus RNA in their seminal fluid after 83 days and 193 days after discharge, respectively.