A study published yesterday in Emerging Infectious Diseases describes prolonged shedding of Oropouche virus RNA in a symptomatic traveler's whole blood, serum, and urine, while viral replication was detected in semen 16 days after infection, which the authors say suggests a risk of sexual transmission.
Oropouche virus, an emerging zoonotic arbovirus, is spread mainly by biting midges and Culex quinquefasciatus mosquitoes. Infection typically causes influenza-like symptoms but can lead to short-term meningitis or meningo-encephalitis. Endemic to the Amazon region of South America, the virus has also caused travel-related outbreaks in the Caribbean, Europe, and the United States, where 90 cases have been reported by five states, mostly in Florida.
Oropouche's link to rare but notable adverse pregnancy outcomes in Brazil in 1982 and 2024 bears a worrisome resemblance to that of another tropical mosquito-borne virus, Zika, which causes abnormally small head size in infants.
Ability to replicate no longer seen by 32 days
On August 2, 2024, the 42-year-old Italian case-patient, who had traveled to Cuba in July, sought medical care for an acute illness. The day before he returned from Cuba, he began experiencing a fever of 39.0°C (102.2°F), headache, and general malaise. The fever lessened after 2 days but returned 2 days later. No meningeal irritation was observed, and blood culture was negative for Zika and two other mosquito-borne viruses, dengue and chikungunya.
Reverse transcription polymerase chain reaction (RT-PCR) testing of serum, whole-blood, and urine samples collected 4 days after symptom onset revealed a diagnosis of Oropouche fever. By day 10, the patient had recovered completely.
RT-PCR remained positive in whole-blood and urine samples collected 10, 16, and 32 days after symptom onset, while serum was positive for Oroupouche RNA at 10 but not 16 days. RNA was detected in semen and whole blood, but not urine, on days 16 and 58.
Infectious Oropouche virus was cultured on day 16, with viral replication confirmed by the observation of clear cytopathic effects after 5 days and elevated viral RNA concentrations in spent cell growth medium. Higher levels of RNA were still being shed in higher levels in semen than in serum and whole blood on day 32, but the ability to replicate could no longer be established.
Possible effects on sperm banking, assisted reproduction
The researchers noted that prolonged viral shedding in semen has been documented for 40 viruses, namely Zika and Ebola.
Because we did not separate seminal fractions, we cannot establish an association with the cellular fraction or spermatozoa.
"Detectable OROV [Oropouche virus] RNA in semen could result from replication in the male genital tract but also from passive diffusion of OROV," they wrote. "In the patient we report, blood could not be excluded as a cause for a positive RT-PCR in semen, but cross-contamination from urine seems unlikely because OROV RNA shedding persisted longer in semen than in urine."
The authors urged caution in interpreting the study findings. "Because we did not separate seminal fractions, we cannot establish an association with the cellular fraction or spermatozoa," they wrote. "Failure to isolate RT-PCR–detectable OROV from semen does not exclude the possibility of prolonged shedding of infectious virus."
The results, the researchers said, raise concerns over the possible sexual transmission of Oropouche virus and could have implications for sperm banking and assisted reproduction.
"Pending further evidence (e.g., longitudinal studies to establish the frequency and kinetics of infectious OROV shedding in semen to assess its clinical relevance), we recommend use of barrier protection when engaging in sexual intercourse if OROV is confirmed or suspected," they concluded.
