Sexual transmission was confirmed for nine of the 22 viruses studied, including Ebola, Zika, and mpox, making it a key factor in ongoing disease spread.
A recent systematic review, published in The Lancet Microbe, reveals insights into the persistence of viruses in human semen following acute infection. The study underscores significant implications for ongoing disease transmission, male reproductive health, and the development of vaccines and treatments. Conducted in accordance with PRISMA guidelines, the review analyzed 373 studies, drawn from a screening of 29,739 articles across five major databases.
Among the viruses analyzed, Ebola exhibited the longest persistence, with detection in semen up to 988 days after discharge from an Ebola treatment unit and 965 days after illness onset. Zika virus persisted for up to 941 days, with a median persistence of 57 days. Other viruses, such as yellow fever, West Nile, and dengue, showed varying durations of semen persistence, ranging from 21 to 37 days. In contrast, Kyasanur Forest disease virus persisted for only 8 days. These findings highlight the variability in viral persistence, both between viruses and individuals, complicating efforts to predict infectious risk.
The study highlights the variability in the duration of viral persistence in semen. As noted by the investigators, “In addition to variation between different viruses, considerable person-to-person variability was also found. In cases with sufficient data, the median length of detection was often considerably shorter than the maximal detection time; this distinction is of central importance to public health recommendations and clinical guidelines.” This variability complicates the ability to predict infectious risk and highlights the importance of both maximal and median detection times for accurate public health recommendations.
Of the 22 viruses studied, nine showed evidence of sexual transmission. Viruses like Zika, Ebola, and mpox can be transmitted sexually, with Ebola exhibiting the longest known persistence in semen. The study underscores the need for a deeper understanding of both maximal and median persistence times in order to make accurate public health recommendations and prevent disease transmission. Additionally, the review identifies critical research gaps, particularly in the dynamics of viral persistence, the role of sexual transmission in emerging diseases, and the implications for vaccine development and public health interventions.
22 viruses were detected in human semen, with 9 showing evidence of sexual transmission.
Ebola and Zika had the longest persistence in semen, up to 988 and 941 days, respectively.
Research gaps remain in understanding viral persistence, sexual transmission, and implications for public health.
Zika typically causes mild symptoms, including fever, rash, joint pain, headache, and conjunctivitis, usually appearing 2 to 7 days after exposure. While many cases are asymptomatic or mild, Zika can be particularly concerning in pregnant women due to its potential to cause birth defects like microcephaly in the fetus.2
Ebola disease presents initially with "dry" symptoms such as fever, muscle aches, severe headache, and fatigue, appearing 2 to 21 days after exposure (typically 8 to 10 days). As the disease progresses, "wet" symptoms develop, including gastrointestinal issues (nausea, vomiting, diarrhea), unexplained bleeding, and confusion. Severe cases may lead to multi-organ failure. Survivors may experience long-term complications, such as fatigue, vision problems, joint pain, and mental health issues like depression and PTSD.3
In conclusion, the review highlights the role of understanding viral shedding through semen in controlling infectious disease spread. As new pathogens with pandemic potential emerge, further research into viral persistence is essential for improving global health strategies and preventing future outbreaks.
